UC RIVERSIDE
ENTOMOLOGY

URBAN ENTOMOLOGY

by
Walter Ebeling

Chapter 6
Pests On or Near Food

Summary | ANT Species | COCKROACH Species | FLY Species | Figure Captions

Contents of Chapter

Cockroaches

Flies

Ants


Summary
This chapter deals with three of the most important groups of household pests - the domestic species of the cockroaches, flies, and ants. These are insects whose habits are such that they commonly come in contact with food or crawl about on surfaces on which it is placed, such as shelves, sinks, and breadboards. Cockroaches and flies are known to be mechanical carriers of many kinds of disease germs.

COCKROACHES


Cockroach Species List

Cockroaches are flattened, fast-running, nocturnal insects that seek warm, moist, secluded areas. They are of ancient origin, and have not changed much during the 400 million years since the Devonian period of the Paleozoic era (Jeannel, 1960). They are gregarious and, because they develop from egg to adult by gradual metamorphosis, all stages and instars are found together in their preferred harborages. Cockroaches are now placed in a separate order: Dictyoptera.

These are among the most important of the household pests. In a survey of 8 large housing projects in North Carolina, 2 in each of 4 cities, cockroaches were found in 76.7% of the apartments in which control work was done by project maintenance men and in 12.7% of those that were regularly treated by licensed pest control operators (Wright, 1965a). Cockroaches are also known to cause severe injury to plants and their fruits, particularly in greenhouses (Roth and Willis, 1960).

This group of insects is well known to biology students because, like grasshoppers, they are commonly chosen for laboratory demonstrations of a somewhat generalized type of external and internal insect morphology. They are also commonly reared for research purposes, e.g., as test insects in the investigation of new insecticides. Nearly every entomological research group continuously maintains a culture of 1 or more species of cockroaches.

It is fortunate that during the last decade, insects of such great importance as the cockroaches, not only as pests, but also as experimental animals in teaching and research, have become the subjects of some excellent books containing a wealth of information of both academic and practical importance.In The Biology of the Cockroach (Guthrie and Tindall, 1968), one chapter deals with insecticides and control. Likewise, The Cockroach (Cornwell, 1968) has thus far appeared as Volume I which contains "An account of the biology oi the more common species, including details of their structure, physiology, behavior, and ecology." Volume II is expected to be published in 1975, and will be devoted to cockroach control methods. It should be available by the time our present book has been completed.

Cockroaches as the Ancestors of Termites

Certain morphological, biological, and behavioral characteristics of cockroaches indicate that they were the ancestors of termites, which appeared much later in the scale of geological time. These characteristics include the possession of intestinal protozoa (flagellates) by the primitive wood-eating cockroaches, Cryptocercus punctulatus and Panesthia javanica, the former being indigenous to the United States. These protozoa convert indigestible cellulose into soluble sugar, as they do in the more primitive families of termites (Trager, 1932; Cleveland et al., 1934; Rau, 1941). Of interest in this connection is the observation by Snyder (1935) that C. punctulatus and the termite Zootermopsis were found in California inhabiting the same log. Cockroaches and primitive termites also have intracellular symbionts (Brooks and Richards, 1955). This has led to the idea that the common ancestors of cockroaches and termites had both intracellular microorganisms and xylophagous flagellates. Cockroaches, except for the genus Cryptocercus, have retained the intracellular symbionts, and Cryptocercus has retained the intestinal flagellates. The primitive living termites (all the families except Termitidae), except for Mastotermes darwiniensis Froggatt, the most primitive of them all, have kept only the intestinal flagellates (M. darwiniensis has both). The Termitidae have lost the xylophagous intestinal flagellates, but have acquired a rich and complex bacterial fauna (GrassÚ and Noirot, 1959).

Mastotermes darwiniensis has an egg mass similar in appearance to the egg capsule (o÷theca) of cockroaches. Its eggs are firmly cemented together by a light-brown, gelatinous secretion that fills the interstices (Hill, 1925; Snyder, 1935).

The ability many cockroaches have to mix bits of debris with mouth secretions in order to hide or disguise their o÷thecae reminds one of a similar process used by termites to build nests. There are other interesting similarities (Rau, 1941; McKittrick, 1964, 1965; Cornwell, 1968).

Cryptocercus punctulatus leads a subsocial life in decayed logs, which serve as both food and shelter (Snyder, 1935). An Australian cockroach, Panesthia, lives in distinct family groups in burrows in the soil. Each group consists of an adult male and a viviparous female, and from 10 to 20 nymphs in various instars. Soon after reaching maturity, the adults bite off their own tegmina and hindwings; wings are inconvenient for insects that inhabit burrows. This indicates the probable origin of termites' social life in subterranean galleries and their discarding of wings (Tillyard, 1926). The subsequent evolution of termite social organization to such an astounding degree of complexity, superficially so strikingly similar to that of the social Hymenoptera, depended on a concomitant chemical evolution of pheromones and a highly specialized chemical communication among these insects. This is a good example of the important role of pheromones in insect evolution.

The ancient cockroaches folded only a small area (anal lobe) of their hindwings, as can be seen in the fossil genus Pycnoblattina. The living Mastotermes darwiniensis also folds the anal lobe of its hindwings. The cockroaches gradually evolved more complex folding of the hindwings, while the termites, except for M. darwiniensis, completely lost this feature of their wing structure (Tillyard, 1936, 1937; McKittrick, 1964). McKittrick (1965) believed that cockroaches, walkingsticks, and termites belonged in the same insect order. She pointed out that Cryptocercus had xylophagous flagellates in common with primitive termites but not with other cockroaches. On the other hand, the primitive Mastotermes darwiniensis has intracellular bacteriocytes in common with cockroaches, but not with other termites. Also, in certain morphological features, Cryptocercus differs far less from Mastotermes than it does from many of the cockroaches.

The Place of Cockroaches in the Class Hexapoda

The place of cockroaches in the class Hexapoda has been the subject of considerable disagreement among experts during the last half-century. All the common cockroaches were formerly considered to be members of the family Blattidae of the order Orthoptera. This order included, besides the cockroaches, the grasshoppers, crickets, katydids, mantids, walkingsticks, and several other related families. In recent years, several new classifications have been proposed. The author has adopted the classification used by Cornwell (1968), based on the one suggested by Imms (1957) in the ninth edition of his A General Textbook of Entomology. According to this classification, the cockroaches should be placed in the order Dictyoptera, which is divided into the suborders Blattaria (cockroaches) and Mantodea (mantids). Blattaria in turn is divided into the superfamilies Blattoidea and Blaberoidea. Blattoidea contains 2 families, one of which (Blattidae) includes the well-known genera Blatta and Periplaneta. Blaberoidea contains 3 families, one of which (Blattellidae) contains the genera Blattella and Supella.

One way in which cockroaches differ from the closely related grasshoppers, locusts, and crickets is that they do not have a visible ovipositor. Also, they do not lay their eggs singly or in pods, but in a hardened, purseshaped egg case called the o÷theca (plural, o÷thecae). Most domestic cockroaches drop their o÷theca as soon as it is formed, but the German cockroach (Blattella germanica), generally the species most frequently found in the household, carries hers until a day or two before the eggs are ready to hatch. She is often seen with an attached o÷theca (figure 148).

Among domiciliary cockroaches, B. germanica is the only species with an o÷theca subject to desiccation. The eggs are dependent on moisture supplied by the mother. The o÷thecae of other species are remarkably resistant to desiccation. Pryor (1940) believed the o÷theca of Blatta orientalis to be covered with an oily secretion, probably derived from the cuticle of the mother. It was so effective in retarding water loss that eggs hatched in about 46 days from o÷thecae that had been kept in an atmosphere of 0% relative humidity from the age of less than 1 day (Roth and Willis, 1955).

O÷thecae also effectively protect the enclosed eggs from insecticides. Not until the eggs are hatched and the nymphs leave the protection of the o÷theca and crawl over the insecticide residue are they subjected to the effects of an insecticide treatment, provided the residue retains its efficacy that long.

World-Wide Distribution of Cockroaches

Cockroaches are tropical or subtropical in origin, and can maintain themselves outdoors in such areas. Species that became adapted to living in human habitations - "domestic" or "domiciliary" species - all originated in north or tropical Africa. Species names such as americana, australasiae, germanica, or orientalis, and the corresponding common names, are therefore misleading.

The distribution of domiciliary cockroaches throughout the world was made possible by their ability to infest the various means of intra- and intercontinental transport, particularly ships. Originally, and probably to this day, their principal means of transportation between continents has been by ships. (Movie fans and readers of classics may be interested in the fact that in 1792, the much-maligned Captain Bligh combated cockroaches on HMS Bounty with boiling water.) However, transport of cockroaches in the baggage compartments and kitchens of aircraft has been abundantly documented (Roth and Willis, 1960).

For many years, the principal species infesting ships was the American cockroach, but in more recent times the German cockroach has become the dominant ship-infesting species (Cornwell, 1968).

To judge by the enormous numbers of cockroaches infesting ships before the advent of effective insecticides, these insects must have found abundant food and water. Even without food and water, however, cockroaches can live for considerable periods. Newly emerged adult females of the German cockroach, Blattella germanica, have been found to live at 27░C (81░F) and 36 to 40% relative humidity for an average of 20.1 days without food or water, 14.7 days with dry food (dog biscuits) and no water, 35.1 days with water but no food, and 82 days with both food and water. The corresponding figures for the American cockroach, Periplaneta americana, were 41.7, 40.1, 89.6, and 190 (Willis and Lewis, 1957). The apparent ability of the 2 species to survive slightly longer without food and water than with dry food alone is interesting, but in any case, cockroaches are well adapted to dispersal over great distances by man, even when food and water are lacking.

Domestic species of cockroaches never or rarely fly, but are readily carried about in and on such items as sacks, cartons, or packages (particularly corrugated cartons) of food, in laundry, or in kitchen appliances and furniture. Beverage cartons are particularly important means of distributing cockroaches. The cartons are often contaminated with spilled syrups or malts, which attract cockroaches. Empty and unrinsed softdrink or beer bottles in night clubs, restaurants, markets, and homes form a part of the infestation chain. More than 200 cockroach nymphs have been found in a single soft-drink bottle brought to a market for exchange (DeLong, 1962). Cockroaches may be found by the thousands in insulation in the walls of refrigerators and gas or electric ranges, surviving for months if necessary without access to their usual foods and feeding only on cast skins and dead insects. Cockroaches may become established in basements or crawl spaces, particularly, if these places are dark and damp, and they may then enter the building around utility pipes, air ducts or ventilators, or under doors.

Economic Importance of Cockroaches

Cockroaches rank with termites as the most important insects that must be dealt with by the owners or occupants of homes or other buildings or by pest control operators hired to combat insects. Flies and mosquitoes may be more important as household pests in some areas, but they breed elsewhere and then invade dwellings. Therefore, in the United States and many other countries, fly and mosquito control is generally considered to be primarily a community or regional responsibility, and the homeowner is generally left with the job of controlling only minor or seasonal infestation.

The Cockroach as a Domestic Nuisance

Cockroaches breed within the home, sharing with man his food, water, shelter, and warmth, and are thus active throughout the year. They consume any human or animal food or beverage, as well as dead animals and plant materials, leather, glue, hair, wallpaper, fabrics, and the starch in bookbindings. They contaminate food, imparting an unpleasant odor and taste, and may transmit disease organisms.

Although cockroaches are nocturnal, if they are abundant a few of them may be seen during daylight hours, particularly if articles in pantries, cabinets, and closets are moved about to disturb their hiding places. Other evidences of a cockroach infestation may be dead cockroaches, cast skins of the various nymphal instars, empty egg cases, and fecal droppings. The droppings are variable in size, and range from as small as "flyspecks" to as large as mouse droppings. Intersections and corners of shelves and the hinges of cabinet, pantry, and even closet doors show fecal stains when there are heavy infestations. The musty odor left on objects cockroaches contact may also be evident in heavy infestations.

Cockroaches as Disease Carriers

Many of the organisms causing diseases of man have been found on the tarsi and other body parts, or in the fecal pellets, of cockroaches, but these insects are most commonly implicated in the transmission of Salmonella, the causal agent of food poisoning (Roth and Willis, 1957, 1960; Rueger and Olson, 1969). When the feces of American cockroaches infected with Salmonella oranienburg were spread on human foods and on glass, the bacteria survived for the following periods: on corn flakes, 3.25 years; on crackers, over 4.25 years; and on glass slides, over 3.67 years. Mice placed in jars containing minute quantities of infected cockroach feces became themselves infected in as brief a period as 1 day (Rueger and Olson, 1969).

Parasitic toxoplasmosis is a disease that is believed to infect more than a third of all adult Americans at some time during their lives. It is usually a mild disease, but can be extremely serious in pregnant women, causing congenital defects in an unborn child while remaining mild or symptomless in the mother. The protozoan parasite, Toxoplasma, can be acquired by eating infected raw or undercooked meat. If the blood serum of an infected person is added to cultures of the parasites, the differing colors of fluorescence of the latter will indicate either a positive or negative reaction and thereby serve as a test for the disease (Anonymous, 1973a).

Cats that consume birds or rodents carrying the parasite can become carriers. Filth flies have been found capable of transmitting infectious Toxoplasma o÷cysts to human food 1 or 2 days after consuming infected cat feces. In laboratory tests, Toxoplasma parasites were isolated from the digestive tracts and feces of cockroaches as long as 7 and 10 days, respectively, after the cockroaches had last been in contact with infected cat feces. Filth flies and cockroaches might consume infectious cat feces and contaminate human food. They might also serve as food for birds and small rodents that could in turn be eaten by cats (Anonymous, 1973a).

Goodwin (1973) recorded the successful passage of hepatitis B antigen (AB-Ag) through the alimentary tracts of American cockroaches, and identified the antigen in the feces of the insects. The hepatitis antigen was found in the feces of the cockroaches for up to 9 days after their initial exposure to the antigen-positive test meal.

Cockroach Bites

Roth and Willis (1957) discussed 20 reports of cockroaches biting man. However, such instances are rare and not serious; they are discussed here only because questions are often asked concerning the biting ability of cockroaches. There have been a number of reports in the literature of cockroaches being so numerous in ships that they gnawed the skin and nails of the men on board; in one case, the sailors wore gloves while sleeping to prevent hordes of the insects from gnawing off their fingernails (Roth and Willis, 1960). Cockroaches are most likely to gnaw fingernails, eyelashes (of sleeping children), and the callused portions of hands and feet, but can also cause small wounds on softer skin. Periplaneta americana and P. australasiae are the species most often implicated.

The Cockroach Allergen

Some people are allergic to cockroaches. In one investigation among 253 normal persons, 7.5% showed positive skin tests with extracts of cockroaches (Periplaneta americana and Blatta orientalis) compared with 28% of an unselected group of 114 allergic patients. Skin-sensitizing antibodies were present in the blood sera of positive reactors. The allergen is thermostabile. There is evidence that in some instances symptoms attributable to food allergy may be caused by cockroach allergen with which the food is contaminated (Bernton and Brown, 1964, 1970a, b).

In an investigation to test the age of onset of skin reactivity, 38 out of 102 allergic children, ranging from infants to 12 years old, gave positive cutaneous reactions to body extracts of the German cockroach, Blattella germanica, compared with only 5 out of 100 nonallergic children. A 4-year-old asthmatic child was the youngest to give a positive reaction (Bernton and Brown, 1970a). In a later investigation, it was found that an extract of B. germanica caused an attack of asthma in 10 asthmatic persons with skin hypersensitivity to the extract and other allergens, but not in asthmatics without such skin hypersensitivity (Bernton et al., 1972).

An allergen in the feces of B. germanica acts as an ingestant when it contaminates food and as an inhalant when dried fecal particles become incorporated with house dust (Bernton and Brown, 1970b).

Natural Enemies of Cockroaches

Natural enemies appear generally to be of little importance, although according to Roth and Willis (1960), E. C. Zimmerman stated that the hymenopterous egg parasite Comperia merceti (Compere) (Encyrtidae), when accidentally imported, practically wiped out the brownbanded cockroach in Hawaii. In some parts of Honolulu, almost 100% of the o÷thecae of this species were parasitized. Muesebeck et al. (1951) recorded this parasite from the German as well as the brownbanded cockroach in Florida and Texas. Flock (1941) stated that another related parasite, Anastatus blattidarum FerriŔre (Eupelmidae), seemed to be effective in controlling the brownbanded cockroach in certain areas in Arizona, and Hull and Davidson (1958) found some o÷thecae of this species to be parasitized by A. blattidarum among the cockroaches they reared in Ohio. T. Maki considered the hymenopteron Tetrastichus hagenowii (Ratzeburg) (Eulophidae) to be an important egg parasite of cockroaches in Taiwan (Roth and Willis, 1960), and Muesebeck et al. (1951) recorded Blatta orientalis, Blattella germanica, Periplaneta americana, and P. australasiae as hosts in Florida and Louisiana.

Roth and Willis (1960) also stated that species from at least 6 families of Hymenoptera had been recorded as developing on cockroach eggs. They quoted Edmonds (1957) as stating that evaniid egg parasites were so abundant in a home in Ohio that the occupants considered them a nuisance, although the oriental cockroaches in the basement did not annoy them. Roth and Willis also listed many predators, including scorpions, spiders, dragonflies, mantids, bugs (e.g., reduviids), beetles (carabids, rhipiphorids [similar to mordellids], dermestids, and others), wasps, ants, toads, frogs, lizards, birds, poultry, and various mammals. Cannibalism among cockroaches, including the devouring of o÷thecae, has been noted by many investigators even when food was adequate.

When humidity is too high in cockroach culture colonies, mites may become numerous, and have been known to cause German cockroaches to drop their o÷thecae prematurely, resulting in a low percentage of eggs hatching. Control of mites with acaricides has been known to increase the vigor of cockroach colonies (Roth and Willis, 1960). A pterygosomid mite Pimeliaphilus podapolipophagus Trňgňrdh, must actually feed on live cockroaches to survive; it cannot subsist on feces, cast skins, or dead insects (Cunliffe, 1952). It has been accused of biting people, and its presence in homes is an indication of cockroach infestation (Baker et al., 1956).

Roth and Willis (1960) reported 2 species of spiders in the family Theridiidae, the South African Latrodectus indistinctus and the North American L. mactans, the latter the venomous "black widow," as predators of cockroaches. The author observed another theridiid spider, Steatoda grossa (C. L. Koch) (figure 212, chapter 9), which resembles the black widow but is one of its natural enemies, in great abundance in an infestation of German cockroaches confined to experimental mockup closets at the University of California (Los Angeles). Remains of cockroach nymphs were found in their webs. It is also of interest to note in this connection that the related S. fulva (Keyserling) blocks the nest entrances of the harvester ant Pogonomyrmex badius (Latreille) during the early afternoon, when temperatures are high and the ants are inactive, and feeds on the ensnared ants (H÷lldobler, 1970). Steatoda albomaculata (De Geer) also feeds on ants (Levi, 1957).

From their extensive review of the literature, Roth and Willis (1960) concluded that with the exception of a few instances of egg parasitism such as just cited with respect to Comperia merceti and Tetrastichus hagenowii, there had been too little information to enable them to evaluate the effectiveness of biological control in reducing the numbers of pest cockroaches, and that further investigation would be justified.

A large percentage of any cockroach population generally contains internal parasites. Two species of nematodes and 7 of protozoan parasites were found in 105 Blattella germanica in New York city.

One of these nematode species, Blatticola blattae (Graeffe), was present in 96.2% of the cockroaches collected. Among the protozoa, Nephridiophaga blattellae was found in 82.8% of the cockroaches, and 3 other species were abundant (Tsai and Cahill, 1970).

Rearing Cockroaches Experimentally

A continuous supply of several species of cockroaches has been reared for experimental purposes in our laboratory at UCLA. These species are, in the order of what we consider to be their importance in California, the German, oriental, brownbanded, and American cockroach. Later the Australian and the brown cockroach were added. The insects were originally reared in 15 gal (57-L) garbage cans with an electric barrier (Wagner et al., 1964), later replaced by 20-gal (76-L) plastic trash cans (Ebeling et al., 1966). A double layer of strips of aluminum foil with a strip of insulation tape between them, and with the terminals from a 22.5-volt battery connected to the aluminum strips, serves as an electrified barrier to the escape of the cockroaches. In each trash can there is a poultry-watering device, Purrina Dog Chow, and 3 mazes of concentrically rolled and closely approximate layers of corrugated paper to serve as the harborage areas that cockroaches require for optimum development. The trash cans are covered with their usual plastic lids, provided with screens for ventilation.

It is important to prevent contamination of a colony by stray individuals of other species. It is especially important to keep German cockroaches out of colonies of other species because of the ability of this insect to thrive and rapidly increase its numbers at the expense of the others.

In the cockroach rearing room, boric acid powder applied under benches, radiators, appliances, cabinets, etc., will serve to permanently prevent a buildup of the cockroach population, in the rearing room and adjacent rooms, from those insects which escape when they are being removed for experimental work.

Twenty cans of German cockroaches and a can or more of each of the other 5 species are continuously maintained in our laboratory. The temperature is kept near 80░ F (27░ C) in the rearing room. Provided that a water supply is constantly maintained, the author and his colleagues have had no indication that the maintenance of relative humidity above ambient is of any advantage in the rearing of cockroaches, at least in the rearing cans just described. With ambient humidity and monthly removal of the debris at the bottoms of the cans (with a vacuum-cleaner device), infestation of German cockroaches by parasitic mites has been avoided. American cockroaches drop their egg cases to the bottoms of their rearing cans; therefore, the cans are vacuumed only about twice a year, but their colonies do not produce so much debris and do not seem to be so susceptible to mite infestation as those of the German cockroaches.

German Cockroach, Blattella germanica (L.) (Blattellidae)

The German cockroach is generally the most important cockroach species in the United States and many other areas of the world in homes, apartment buildings, restaurants, and in the food preparation and food-storage rooms of hotels, hospitals, and other private and public buildings in which food is prepared, stored, or served.

Description. Adult German cockroaches are 1.3 to 1.6 cm long, pale brown or tan, and have 2 parallel dark streaks on the pronotum (plate III, 1). They have chewing mouthparts. (See figures 44and 45, chapter 4, showing the similar American cockroach.) Their movements are very rapid when they are disturbed. They are nocturnal. If a few are seen crawling about in open spaces during daylight hours, this indicates that the infestation is already severe. The female is darker and has a broader abdomen than the male, and is rounded posteriorly. If German cockroaches are placed on their backs, the males are easily distinguished by the yellowish, slender abdomen, tapering gradually to the posterior end. The abdominal cerci of the males have 11 segments and those of the females have 12.

In their investigation of the German cockroach, Willis et al. (1958) found the ratio of females to males to be 1.12:1. In similar work, Ross (1929) observed that the sexes occurred in approximately equal numbers.

Mating Behavior. Roth and Willis (1952) determined that the male of the German cockroach could not detect the female from a distance, even when in close proximity, but had to make physical contact, ordinarily via the antennae. The antennae of the female, as well as other body regions, contain a chloroform-soluble, nonvolatile substance that will stimulate the male sexually. Thus, sex discrimination by males is mainly owing to "contact chemoreception." It follows that the male German cockroach probably cannot be attracted from a distance by means of synthetic sex attractants (provided they are available) as some other insect species can be.

When male and female meet, their antennae touch and vibrate against each other. The male then turns around, raises his wings to expose the orifices of a pair of dorsal glands located on the seventh and eighth tergites, and extends his abdominal segments to expose the openings of the 2 pairs of glands. The glands are not normally visible, being covered by the wings and by the margins of the preceding abdominal sclerites. Both wing-raising and extension of the abdomen are required to uncover the glands. The female eats a secretion from these glands. After she has fed for a few seconds, the male-pushes his abdomen farther back, and connection of the genitalia is made. The male then moves out from under the female, and the pair remain attached in a linear position for an average of about 86 minutes (Roth and Willis, 1952). These authors also pointed out that the fact that German cockroaches do not need to be attracted from great distances, as do many other insects for the meeting of sexes, is understandable in view of the habits of cockroaches in general. The chance meeting of opposite sexes is enhanced by the fact that they are negatively phototactic and positively thigmotactic (principally guided by contact), and that they are gregarious, with large numbers seeking the same environment. They seek secluded and particularly very narrow hiding places, such as cracks, crevices, and voids, especially those having optimum temperature and moisture conditions. Attraction to the odor of the species is another factor that favors aggregation. Once the sexes have been brought together by these different stimuli, more refined stimuli lead to sexual discrimination.

Life Cycle. The German cockroach lays more eggs and has more generations per year than the other common domiciliary species, and therefore tends to increase in numbers much more rapidly. There may be 3 or 4 generations per year. In one investigation at a temperature of 76░ F (24.4░ C), the developmental period varied from 54 to 215 days, with an average of 103 (Gould and Deay, 1940). It has been found to be as little as 60 days for males and 65 days for females at 95░ F (35░ C) and 90 to 95% relative humidity (Ross, 1929). An individual German cockroach, however, lives an average of 200 days at room temperature (Gould and Deay, 1940), and may live as long as 10 months (Truman, 1961a). A comparison of the developmental periods of the 4 principal domiciliary cockroaches at 82░ F (28░ C) and at ordinary room temperature is shown in figure 149.

The O÷theca (Egg Capsule). The German cockroach female produces her first o÷theca 11 or 12 days after becoming an adult (Ross, 1929). 0÷thecae can be produced parthenogenetically (without fertilization), but although embryos develop, the eggs do not hatch (Roth and Willis, 1956). Unlike other domiciliary species, the German cockroach female carries her o÷theca for as long as a month, until a day or two before the eggs are ready to hatch, then drops it anywhere. The eggs occasionally hatch while the o÷theca is still attached. The female generally deposits 4 or 5 o÷thecae, but there can be as many as 8. The females of other cockroach species drop the o÷theca as soon as it is fully formed. Thus, the abundance of females with their attached, brownish, purseshaped o÷thecae (figure 148) is a characteristic of a German cockroach infestation.

The o÷theca is about 8 x 3 mm-rather large in relation to the size of the female. As with all common cockroach species, the eggs are located in 2 parallel rows. The locations of the eggs are indicated by corresponding divisions on the outer wall of the brownish o÷theca. When the embryos have developed to the point where they exert enough pressure, the o÷theca splits open at the top and the nymphs wriggle out. The female will eat the young nymphs if no water is available to her (Ross, 1929).

There are usually 30 to 40 eggs per o÷theca, but there can be as many as 48. In one investigation, an average of 29.9 nymphs were hatched per o÷theca in an average of about 28 days at ordinary room temperature (Gould and Deay, 1940), while in another investigation at 95░ F (35░ C), eggs hatched in 14 days (Ross, 1929). After the fourth o÷theca is produced, the number of eggs per o÷theca gradually decreases to about 75%of the original number in the seventh and eighth o÷thecae (Willis et al., 1958).

The eggs become desiccated if the o÷theca is removed from the female any time before its normal time to drop, for they must obtain moisture from the body of the mother. The end of the o÷theca that is attached to the female is relatively soft and permeable to water, and is not so heavily sclerotized as the posterior end. Roth and Willis (1955) found that German cockroach o÷thecae placed with their anterior ends on wet filter paper gained weight, whereas those with their posterior ends on the same wet paper lost weight, even though the humidity was high in the covered petri dish in which the o÷thecae were kept. Probably, the wall of the o÷theca in contact with the female's genital pouch is permeable to water (Ross, 1929; Parker and Campbell, 1940).

Even before the o÷theca begins to emerge, the abdomen of the female is greatly distended. Once the translucent tip of the o÷theca becomes visible, the entire o÷theca will be fully developed and entirely visible by the following day, changing from white to pink within a few hours. Within a day or two, it becomes light brown and finally chestnut. It is turned with the keel to the left or right (Haber, 1919; Gould and Deay, 1937, 1940).

Nymphal Instars. Wright (1968) found that among 749 German cockroach nymphs, 5.7% emerged while the o÷thecae were still attached to the body of the female, 92.9% emerged within 24 hours after the o÷thecae were dropped, and only 1.4% emerged thereafter. Among field-collected German cockroaches, 27.9 nymphs per o÷theca emerged from those dropped by females collected in summer, compared with only 9.7 from those collected in winter.

German cockroach nymphs have 6 or 7 instars. As in the case of all insects with gradual or incomplete metamorphosis, there is no abrupt change in appearance between immature and adult forms, except that the adults have wings. Nevertheless, the layman will not necessarily associate the tiny, newly hatched German cockroaches or even the more mature nymphs with the adult insects unless he sees all instars and stages together in considerable numbers. The smaller nymphal instars are sometimes isolated from the remainder of the colony, particularly when they have gained access to a crack or crevice too narrow for the older nymphs and adults.

The first-instar nymph is only 3 mm long. The body is dark gray to almost black, except for the second and third thoracic segments, which are pale brown. The pale-brown band conspicuously characterizes the first-instar nymph. In succeeding nymphal instars, the light band becomes narrower and extends in both directions to become a median longitudinal stripe (plate III, 7). In its anterior extension, it eventually becomes the median pale-brown stripe dividing the "two parallel dark streaks" (already mentioned) that characterize the pronotum of the adult. The remainder of this stripe is covered by the wings.

Completely white nymphs or adults may be seen in a cockroach colony. These are newly molted individuals that have not yet had time to harden their cuticles and to acquire the normal color for the species.

A high degree of mortality occurs during the molting periods. Ross (1929) found mortality to be about 50% during each molt except for the last, when it was 40%. He found that about half the insects died of natural causes before reaching maturity. Molted skins were quickly eaten by the nymphs that emerged from them or by other cockroaches that happened to be near-by. On the other hand, Willis et al. (1958) found in their cultures that 85% of the hatched insects reached maturity.

Aggregation Pheromone

As already stated, because cockroaches have a gradual metamorphosis, all immature instars may be seen together with the adults. They tend to congregate in a single area, leaving it to search for food and water, then returning. An aggregation pheromone, present in the feces and on the bodies of the insects (it spreads easily on the greasy epicuticular lipid), is responsible for this tendency to aggregate. The gregarious behavior of nymphs favors their growth and development; they do not develop so well when isolated (Ishii and Kuwahara, 1968). Isolated nymphs that could only see or smell the others, or received contact only with the washings of the body surfaces of other nymphs, or with filter paper contaminated with feces, did not grow at the group rate. This indicated that a "psychological factor" affecting the endocrine system by means of tactile stimulation, chiefly via the antennae, was the principal factor involved in growth acceleration (Izutsu et al., 1970).

Effect of Excessive Crowding. The author investigated the effect of crowding in a "choice box," 30 cm square and 10 cm high, with a 12-mm hole at the top of the partition wall between the 2 halves (Ebeling et al., 1966). When there are only 20 to 40 cockroaches in the choice box, most of them will spend nearly all their time in the dark half, for they are negatively phototropic. The insects tend to congregate at the intersection of 2 plane surfaces or in corners. When such areas are filled, the insects will gather in small, scattered groups on plane surfaces. However, despite the aggregation pheromone, German cockroaches have some aversion to being crowded too closely together. They prefer to leave some space between themselves and their neighbors. They sometimes initially display aggressive behavior toward their neighbors when actual physical contact is made. However, if large numbers are forced to occupy limited space, they soon appear to get used to this situation.

When 200 adult male German cockroaches were placed in a choice box, only 11% were in the light half 3 days later, compared with an average of 16.2% in the light halves of 5 choice boxes, each containing 20 adult male cockroaches. On the other hand,, when 959 adult German cockroaches of mixed sexes and 530 nymphs were placed in the dark half of a choice box, they were so crowded that they made physical contact with one another, and in some cases were one on top of the other. They were left that way for 2 hours, and then a cork occluding the 12-mm hole in the partition wall was removed. Large numbers of cockroaches left the dark compartment. On the third day of the experiment, the insects were anesthetized and,counted. Of the live insects, 36.1% of the adults and 41.7% of the nymphs were in the light compartment of the choice box, preferring the light to an excessively crowded condition in the dark. If German cockroaches are found in parts of an untreated building far removed from food and water or from preferred habitats, it is an indication of excessive crowding in their customary harborages.

Crowding in Narrow Spaces. Adult German cockroaches can move about in space only 1.6 mm in width or depth (Wille, 1920). When given a choice among 8 spaces between masonite plaques placed one above the other and ranging in distances from 1.6 to 12.7 mm apart, in 1.6-mm increments, 67% of adult German cockroaches gathered in the 4.8-mm space. When the plaques were vertically arranged, this percentage increased to 85. Only a few adults gathered in the 1.6-mm space (Berthold and Wilson, 1967). In our laboratory we found that only the first 3 instars of a population of all ages of German cockroaches crawled from a light to a dark compartment of a 5-cm-wide wooden box for a distance of 2 cm under a strip of masonite that was only 1 mm above the floor of the box. Only 80% of the adult population (6 males and 2 females without o÷thecae) crawled through a 2-mm aperture in a 24-hour period, even though the insects were driven by hunger and negative phototropism to seek food and darkness. No adults were able to crawl from the light to the dark compartment when the 2-mm aperture was between the wooden partition wall (1 cm thick) and a masonite ceiling.

The author once observed a severe infestation of German cockroaches in the food-storage room of a large "rest home." Leaking or spilled packages of flour, cereal, or similar foods on the shelves provided plentiful food for the insects. Cockroaches were crowded into a space of 2 or 3 mm between a shelf and the wall. They were completely hidden from view, except for a continuous band of waving antennae that extended from the aperture, and could be seen by looking beneath the shelf.

This.sort of thing is a common occurrence, well known to pest control operators. However, it appears that the first mention of this phenomenon in the literature was in P. B. Cornwell's The Cockroach, and figure 150 is taken from his book.

Habitat

In the living space of a house, German cockroaches are most abundant in the kitchen, and this is also true of other domiciliary species. During the day they may be found under stoves or ranges and refrigerators, and in the insulation in the walls of appliances; under the sink and especially in the "dead space" between the sink and the wall; under and behind the water heater, particularly if it is enclosed in a cabinet; in, under, or behind cabinets, pantries, and closets; behind baseboards and moldings; and in other cracks, crevices, and dark, protected areas. They venture forth at night in search of food and water.

German cockroaches are also likely to be found in the bathroom, particularly if the kitchen and bathroom share a common wall, for then they can infest a common wall void and pass from one room to the other via areas surrounding utility pipes or the louvers and razor-blade receptacle of the built-in medicine cabinet. In moderate to severe infestations, they can be found throughout the house in protected areas, such as closets, dressers (usually above the top dresser drawer), sofas, electrical appliances such as radios and television sets, under stairwells, behind moldings, picture frames, etc. All such places must be thoroughly treated with insecticide for effective control.

Television sets in particular are becoming increasingly important harborages for both German and brownbanded cockroaches. Not only the warmth, darkness, and the edible glue used in construction, but often the bits of human food commonly found in the vicinity of television sets are attractive to cockroaches and combine to provide an ideal harborage.

In severe infestations, enormous numbers of German cockroaches may sometimes be found in the attic and in wall voids. They use the wall voids to move either laterally or vertically from one room to another or from one apartment to another. They may also be found in the crawl space under the house, at the bases of foundation walls, in cracks in the sidewalk, in the lawn and under shrubbery, and in outdoor incinerators or garbage-disposal bins.

German Cockroaches Finding New Habitats

Before German cockroaches became almost universally resistant to chlordane in the 1950's, they were known to inhabit kitchen areas almost exclusively. Since that time, they have extended their habitats until they are now often distributed widely throughout the house, at least in the cases of more severe infestations (Shuyler, 1956). This is a characteristic formerly attributed only to the brownbanded cockroach, Supella longipalpa (F.). It may be that because of the switch from chlordane to organophosphorus and carbamate insecticides, German cockroaches were not only more strongly repelled by the latter insecticides, which was easily demonstrated (Ebeling et al., 1966, 1967), but that they were more successful in surviving initial contacts with the toxicants, and found new harborages free of insecticides in a wide variety of locations throughout the infested premises (Ebeling et al., 1968). This new behavior might be inherited because of its survival value.

There are other reasons for the increasing dispersal of German cockroaches throughout a house that arise from changes in furnishings and in man's living habits. Central heating has become common, resulting in temperatures in all areas that are conducive to cockroach breeding, even in winter. Even if some rooms are cooler at night, the insects can find warmth in such appliances as electric clocks, radios, or television sets. Some people eat their meals, or at least light snacks, near the television, which could be in the livingroom, bedroom, or den. A few crumbs, pieces of cookies, etc., can sustain many cockroaches. Many modern homes also provide more sources of water than were formerly found in homes. There may be 2 or 3 bathrooms, as well as air-conditioners with evaporating pans. Beer cans and soft-drink bottles not completely emptied may be left in more locations, now that homes are more extensively utilized than they formerly were, and these also provide sources of both food and water.

Physical Features of the Habitat That Influence Aggregation

The earliest insects had sheltered and restricted habitats that were at least reasonably damp, such as beneath stones and litter or under loose bark, as one might expect on the basis of the relatively poor waterproofing mechanism of their cuticles. Ametabolous or paurometabolous development made a continuously cryptobiotic life style possible. Food and mates were found by chance encounters. It was improved cuticular waterproofing and the development of wings that freed insects from a restricted environment. An improved olfactory sense became advantageous. Eventually, the pheromones and sophisticated chemical communication systems of some of the modern insects were evolved (Moore, 1967).

Among household pests, the silverfish and cockroaches are among the cryptobiotic insects. Although most cockroaches have wings, they use them sparingly or not at all. Accordingly, one might expect that neither silverfish nor cockroaches would be effectively attracted to foods or chemical lures, at least not over distances that might lead to effective chemical trap devices, and this has indeed been found to be true for both these relatively primitive insect orders.

In the case of Blattella germanica and Blatta orientalis, the species aggregation odor was shown to be largely responsible for their gregarious behavior, but the stimulus was effective for only a short distance (Ledoux, 1945). As stated earlier, sex stimulus, although of chemical origin, is limited in cockroaches and requires actual physical contact. Even food odors are only feebly attractive, and will attract German cockroaches only if they occur in areas normally frequented by the insects or in the routes in which they would normally travel. For example, in a room, cockroaches normally travel mainly along wall intersections, the intersections of the floor and the walls, the intersections of the walls and the ceiling, the intersections of shelves and pantry or cabinet walls, and infrequently in other areas.

When experimenting with German cockroaches, Ebeling et al. (1966) found that in a kitchen area in which food was available to the insects, an average of 2.45 per baited trap-jar was trapped in jars placed along the baseboards (intersections of floor and wall), but none in jars placed in the center df the kitchen floor. When all other food was removed from the kitchen, an average of 13.5 insects was trapped in the baited jars placed along the baseboard and 1.15 in the center of the room.

Hunger is one of the factors influencing exploratory activity of cockroaches, but the physical features of a habitat (structural features, temperature, humidity, light) are the principal factors influencing the areas in which the insects will travel.

Factors such as pheromones and food odors can become operative only after these physical features have already attracted the insects. For insecticides or even poison baits to be effective, they must be applied in areas in which cockroaches would normally travel or congregate (Ebeling and Reierson, 1970).

Mass Migratioms of German Cockroaches

These mass migrations have been known to occur without the stimulus of insecticide treatment. For example, Howard (1895) reported a "vast army" of German cockroaches leaving a restaurant on a "dark, drizzly day" and crossing a muddy street to other buildings in a migration that lasted for 3 hours. The migrating insects were nearly all females with o÷thecae. No unusual activity, such as cleaning or insecticide treatment, had taken place in the restaurant. Dr. Howard concluded that this mass movement of cockroaches was a true migration occasioned by overcrowding in the restaurant. Another instance of active migration of German cockroaches from a restaurant to another building was reported by Mielke (1970).

Field Cockroach, Blattella vaga Hebard (Blattellidae)

This species, discovered in Arizona in 1933, is probably of Asian origin, for its nearest relative occurs in India (Hebard, 1935). It may now be found, sometimes abundantly, in irrigated fields and in yards in southern California, Arizona, and Texas, but also sometimes appears in the desert, far from. inhabited or cultivated areas. A severe infestation was found at Oroville, in northern California, in 1967, as recorded by Buxton and Freeman, 1968.

Biology. The field cockroach resembles the German cockroach, and is only slightly smaller. It can be distinguished by the blackish-brown area on the face, from the mouthparts to between the eyes, that is absent from the German cockroach. The 2 parallel, longitudinal stripes on the pronotum of B. vaga are similar to those of B. germanica, but are very dark and more sharply defined. With the aid of a hand lens, the 2 species can be told apart by differences in the subgenital plate (Buxton and Freeman, 1968). The life cycle of B. vaga is similar to that of the German species, but Willis et al. (1958) found an average of only 28 eggs per ootheca, of which 19 hatched, compared with 37 for B. germanica, of which 28 hatched. In B. vaga, after the the third o÷theca is produced, the number of eggs per o÷theca decreases until in the eighth o÷theca it is only 10% of the number found in the first 3. (In the case of the German cockroach, there is a reduction of only about 25%.) Of the hatched insects, 73% reached maturity under laboratory conditions, compared with 85% for the German cockroach.

Habits. The field cockroach is so named because it is ordinarily found outdoors, where it feeds on decaying vegetation, but during the drier seasons, it may invade houses in large numbers. Its feeding habits are similar to those of the German cockroach. Of the 2 species, B. vaga is more likely to be seen during the day, for it is not repelled by light, and in fact is commonly found in the evening around street lights and in display windows. Infestations have been eliminated by removing decomposing plant material from around the foundations of houses (Flock, 1941).

In Texas, a peat control operator who believed he was treating a house for German cockroaches failed to control the infestation. When the insects were found to be field cockroaches, he sprayed the yard, which was the source of infestation, and obtained control (Walter, 1968).

Brownbanded Cockroach, Supella longipalpa (F.)
[=supellectilium (Serville)] (Blattellidae)

This species, like most of the principal domiciliary cockroaches in the United States, is apparently of African origin. It was first recorded in the United States at Key West and Miami, Florida, in 1903, presumably having been introduced from Cuba, where it was known to be abundant even as early as 1862 (Cornwell, 1968). It now probably occurs in all of the United States, with the possible exception of Alaska, particularly in buildings providing moderate to high temperatures. However, it is far less important than the German cockroach as a pest. Even in Egypt, where the species was probably indigenous and where it was called the "furniture cockroach," it was less abundant than either Blattella germanica or Periplaneta americana (Hafez and Afifi, 1956).

Description. The adult brownbanded cockroach (plate III, 2) is approximately the same size. as the German cockroach. The male is 13 to 14.5 mm long, and the female slightly shorter (11 to 12 mm). The abdomen of the female is much broader and more rounded posteriorly than that of the male. The wings of the male cover the abdomen completely, while the wings of the female are short, and never cover the entire abdomen. Males may often be seen flying when a colony is disturbed, but the females cannot fly.

From the dorsal aspect, the adults are dark brown, particularly the head and thorax and the exposed segments of the female, which may in fact range to black. The wings of the female are reddish brown to very dark brown throughout, while those of the male are dark brown at the base, becoming increasingly lighter posteriorly. Both sexes have a band of pale brown at the base of the wings and another band of pale brown a third of the distance from the base, which gives the adults a "banded" appearance. The wings and body of the female are much darker than those of the male. The ventral body surface and legs of the male and the legs of the female are light strawcolored. The lateral margins of the pronotum of both sexes are translucent, and this is also true of a narrower lateral margin of the anterior portion of the wing. The ratio of females to males was found in one investigation to be 1.32:1 (Willis et al., 1958).

Life Cycle. The developmental period of the brownbanded cockroach is considerably longer than that of the German cockroach, as shown in figure 149. The temperature for optimum development is above 80░ F (27░ C) (Gould and Deay 1940), and homes are seldom kept at such high temperatures. Therefore, the biotic potential for the brownbanded cockroach is considerably less than for the German cockroach. In California, it is found in only about 51% as many homes as the Geiman cockroach, but where food is abundant and temperatures are high, the species can become extremely plentiful.

The O÷theca. The females carry their capsules for 24 to 36 hours before attaching them to some object, possibly the kitchen sink, furniture, walls, shelves, bedding, draperies, behind pictures on walls, or other handy places, usually in clusters corners under chairs and tables are among the favored places. Individual clusters (figure 151) on the walls of rearing cans in the author's laboratory have at times contained 50 or more egg capsules. One housewife, in attempting to describe them, said they appeared to be "clusters of seeds". This habit of attaching the o÷thecae to furniture and other household objects results in the species being readily disseminated over great distances. The o÷theca of the brownbanded cockroach measures about 4 x 2.5 mm-the smallest of the common domiciliary cockroach o÷thecae. It varies in color from yellowish to reddish brown. A few days after it is formed, the fertile eggs show greenish through the walls of the o÷theca, and shortly before hatching, the eyes of the young are visible.

The incubation period for the eggs of the brownbanded cockroach was found to be the longest among 6 cockroach species investigated by Gould and Deay (1940). It averaged 49 days at 82░ F (28░ C) and 95.6 days at 72.5░ F (22.5░ C). About 14 fertile o÷thecae were formed per female. The maximum number of eggs normally produced per capsule was 18, but the average number hatching was 13.2.

Nymphal Instars. From the dorsal aspect, the nymphs (plate III, 7) are also basically dark brown in color, but with a narrow, pale margin on the thorax. The meso- and metathorax are pale brown, and the abdomen has a broad, pale area. The dark and pale areas of the nymphs are in striking contrast, and easily identify this species. (The nymphs could more appropriately be called "brownbanded" cockroaches than the adults.) There are 6 to 8 nymphal instars. At room temperature, Gould and Deay (1940) found the average period for nymphal development to be 161 days for males and 162 days for females, but at about 85░ F (29░ C), the average periods were 90 and 95 days, respectively. At room temperature, extremes of developmental periods were 95 and 276 days. The length of adult life varied from 131 to 315 days, with an average of 206 days.

Habits. The brownbanded cockroach was once believed to be unique among domiciliary cockroaches in its tendency to distribute itself throughout a house, even in bedrooms, furniture, and closets, particularly on high shelves, behind pictures on walls, and behind moldings. Gould and Deay (1937) stated, regarding this species: "Except when in search of food, it seldom visits the kitchen, and confines its activities to other parts of the house." About the German cockroach, they stated: "In an infested home, it is confined to the kitchen and lavatories, where it hides behind baseboards, in cupboards, iceboxes, and dark corners, and around water pipes." Apparently, the habits of the 2 species have changed, for now there appears to be no great difference in the way they are distributed in a house or apartment. As already stated, Shuyler (1956) believed the change in the habits of the German cockroach coincided with widespread resistance to chlordane, which in the years following World War II was almost universally used for control of this species. Both species are now most abundant in the kitchen areas, and either can be widely distributed throughout a house or apartment. Sometimes, mixed populations of the 2 species are seen. However, as stated earlier, infestations of brownbanded cockroaches generally occur only in houses or apartments in which temperatures are higher than most people would consider to be comfortable.

Oriental Cockroach, Blatta orientalis L. (Blattidae)

In common with the other important domiciliary cockroaches, the oriental cockroach, despite its name, is believed to have originated in north Africa in areas which combine summer heat and moderate winters (Rehn, 1945). Although in some parts of the world, as in Great Britain (Cornwell, 1968), the oriental cockroach is by far the most important cockroach pest, the German cockroach is much more important in the United States.

In California, the oriental cockroach is found in homes more frequently than the brownbanded cockroach, but does not reach such large numbers or become so widely distributed in the house. Nevertheless, pest control operators report more calls for control of the oriental than of the brownbanded cockroach. Its large size and black color cause it to be regarded as a particularly repulsive pest. The housewife prefers to believe that the insect is a "water bug" or "black beetle" rather than a cockroach, but usually loses no time in calling for the exterminator.

Description. The adult females of the oriental cockroach are about 3 cm long. The male is about 2.5 cm long, and is much narrower than the female. Both sexes vary from dark reddish brown to black, usually the latter (plate III, 3). The female has small, rudimentary, functionless wings, and the male, although it has well-developed wings covering about 75% of its abdomen, does not fly. The tarsi of both nymphs and adults lack an arolium (cushionlike pad between the claws), and there they cannot climb smooth, vertical surfaces. This species is relatively sluggish in its movements. The ratio of females to males has been found to be 1: 1.15 (Willis et al., 1958).

Life Cycle. As shown in figure 149, the developmental period of the oriental cockroach is more than a year, even under indoor conditions, and for some individuals it may be prolonged to about 2 years. The insect may also live for long periods after reaching maturity. Gould and Deay (1940) found that at room temperature, the length of adult lives of 5 females varied from 34 to. 181 days. Among 4 males, the length of adult lives varied from 112 to 160 days. Whereas it may require a long time for an appreciable infestation of oriental cockroaches to develop, enormous populations are eventually possible. Ordinarily, the oriental cockroach does not become so abundant as the German cockroach in buildings, but can become very numerous in secluded places, such as basements or crawl spaces, if they are damp. The species thrives better outdoors than other domiciliary cockroaches in the United States, even under quite severe climatic conditions.

The 0÷theca. The female carries her o÷theca for about 30 hours after it is formed and filled with eggs. It is dropped, or attached to debris or food material, in some protected place. It is large (10 x 5 mm), and when first deposited it is reddish brown and soft, but becomes black, hard, and brittle. Although the number of o÷thecae.formed varies greatly, in an observation of 8 females, the average number was 8. A perfect capsule contained 16 eggs (Gould and Deay, 1940). Another investigator observed that females produced from to 4 o÷thecae, with the usual number being 2 (Rau, 1924). The incubation period was noted to vary from 42 days at 29.5 °Cto 81 days at 21 °C (85 and 70 °F), and was approximately 2 months at the usual room temperatures.

Nymphal Instars. The newly hatched nymph (plate III, 7) is only about 6 mm long, and pale brown. It becomes more reddish with succeeding instars, and finally, in the last instars, dark reddish brown to black, like the adults. At ordinary room temperatures, the period for nymphal development averaged 515 days for males and 542 days for females, whereas at 82 °F (28 °C) it averaged 288 days for males and 310 for females. Willis et al. (1958) found the period for nymphal development at 30░ C (86 °F) to be 164 days for males that had the maximum of 7 instars, and 282 days for females that had the maximum of 10 instars. The oriental cockroach seems to have a seasonal cycle, with the adults appearing in May and June and dying during July (Gould and Deay, 1940; Rau, 1924).

Habits. In the southern areas of the United States, this species has long been known as the one best able to survive outdoors. Its temperature preferences are somewhat lower than those of the German cockroach, and it can thrive in both drier and cooler areas (Gunn, 1935). Like some other cockroach species, Blatta orientalis appears to be changing its habits. It can now survive outdoors farther north than it could originally. Shuyler (1956) observed that oriental cockroaches survived outdoors during 13 weeks of almost continuous freezing weather with a light snow cover. They could be found by moving stones, leaf debris, and clods of soil near a house. About 2 weeks after the arrival of the first warm weather of spring, these insects invaded the house.

Although once known to occur mainly under a house, in the crawl space, basement, or cellar, or on the first floor, particularly around sources of water, the oriental cockroach is now reported with increasing frequency inside at higher levels - as far up as the fifth floor (Shuyler, 1956). In southern California, it is often abundant in the dense vegetation of estates in areas in which some of the cleanest and most elegant homes are located. Its entry into such homes may be purely random movement, generally under sliding glass doors or around utility pipes, air ducts, and ventilators leading from a damp crawl space.

In some localities, oriental cockroaches can be collected at any time of the year from the dark, damp, water-meter vaults that are typically located in the ground in alleys and parkways.

Anything done to increase light, improve air circulation, and decrease dampness in dark, damp basements and crawl spaces will reduce the oriental cockroach infestations, for they can otherwise become established in enormous numbers in such areas.

The "Cockroach Odor." The oriental cockroach possesses in abundance the much-despised "roachy" odor that is associated with cockroaches. Those who believe that everything in nature must serve some useful purpose for mankind will be encouraged by the following account of the alleged usefulness of the "essence" of oriental cockroaches, taken from the 1907 edition of the highly respected Merck's Index:

Constituents: Blattaric acid; antihydropin; fetid, fatty oil. Uses: Internal, in dropsy, Bright's disease, whooping cough, etc. External, as an oily decoction for warts, ulcers, boils, etc. Doses: 10-15 grains in dropsy, as powder or pills, or 4 fluid drams' decoction. (Illingworth, 1915.)

American Cockroach, Periplaneta americana (L.) (Blattidae)

In most areas of the United States, the American cockroach is the least important of the domiciliary species, but in many commercial and certain other large buildings, such as restaurants, grocery stores, bakeries, packing houses, hotels, office buildings, hospitals, and prisons, it is second only to the German cockroach in abundance. In such buildings, these pests commonly infest the basements, food-storage, and food-preparation rooms. They are frequently found in the holds and messrooms of ships. In the United States, this is the predominant species in city sewer systems. In some parts of the world, as in India, Periplaneta americana is the predominant cockroach species rather than Blattella germanica, even in households (Nigam, 1933). The American cockroach occasionally causes injury to greenhouse plants, such as cutting through the stems of seedlings and removing the bark of larger plants (CEIR, 1973).

Description. The adult American cockroach (plate III, 4) is about 4 cm long. The males appear to be considerably longer than the females because their wings extend 4 to 8 mm beyond the tip of the abdomen, while those of the females do not. When 25 males were measured from the tip of the head to the tips of the wings, they were found to average 39.2 mm in length. Measured from the tip of the head to the tip of the abdomen, 25 male American cockroaches averaged 34.3, mm and 25 females averaged 34.4 mm. There was no significant difference in the average width of males (12.2 mm) and females (12.0 mm). (See table 41 under "Brown Cockroach.") The American cockroach is reddish brown throughout, except for a pale-brown or yellow band around the edge of the pronotum. The band is widest at the posterior margin. Both sexes have a pair of slender, jointed cerci at the tip of the abdomen. The cerci of the females have 13 or 14 segments and those of the males have 18 or 19 (Bugnion, 1922). The males have a pair of styli between the cerci. The presence of 2 pairs of appendages at the tip of the male's abdomen, compared with 1 pair in the female, is one of the morphological features separating the sexes. Among laboratory-reared American cockroaches, there have been recorded ratios of females to males of 1:1.07 (Gould and Deay, 1940) and 1.08:1 (Willis et al., 1958). It therefore appears that the sexes may be about equal in numbers.

Life Cycle. The developmental period of the American cockroach is greatly dependent on temperature (figure 149), but it averages about 600 days under ordinary room conditions. After reaching sexual maturity, the average life of the females may be another 400 days (Gould and Deay, 1940).

The preferred temperature for adults and nymphs was 28 °C (82.4 °F), but they remained active at 21 °C (70 °F). At 29 °C (84 °F), the life expectancy averaged over 630 days, but was found to be as long as 1,293 days. The adult life span at 29 °C ranged from 90 to 706 days (average 225 days) for females and from 90 to 362 days (average 200 days) for males (Griffiths and Tauber, 1942).

Under suitable conditions, the longevity and high reproductive potential of the American cockroach may result in enormous populations. This is evident to anyone who has reared the species over a period of years. It is also evident from the great numbers that can be found in sewer systems. As many as 5,000 American cockroaches have been vacuumed from a single manhole in the Los Angeles city sewer system (Wagner et al., 1966).

The O÷theca. The o÷theca (plate III, 4) measures 8 x 5 mm, is brown when deposited, and turns black in a day or two. The lateral indentations marking the locations of the eggs are only weakly indicated. Along the upper ridge of the purselike egg case there is a series of "teeth," marking the location of corresponding eggs, and each tooth has a minute opening at its apex.

The female deposits each o÷theca near a source of food, usually within a day after it is formed, either dropping it or gluing it to a suitable surface with a secretion from her mouth. If the female has the opportunity to do so, she hides the o÷theca with great care in a crevice, or buries it in soft wood or available debris. The o÷thecae of the American cockroach require a high relative humidity for successful hatching (Tsuji and Mizuno, 1971). That may be the reason that in semiarid regions such as southern California, this species is found in large numbers only in damp locations, such as sewer systems, damp basements, the dishwashing rooms in restaurants, and warehouses with inadequate ventilation. Often during the latter part of their lives, American cockroaches deposit their eggs unprotected by an egg case (Gould and Deay, 1940), thus anticipating the egg-laying habit of the descendants of cockroaches, the termites (Rau, 1941). From 15 to 90 o÷thecae (average 57.6) were produced at the rate of about 1 per week, and each contained 14 to 16 eggs. This constituted an enormous production of o÷thecae when compared with most other cockroach species. The average hatch from 534 o÷thecae at room temperature was 13.6 nymphs (Gould and Deay, 1940).

In another similar investigation, an average of only 21 o÷thecae per female was observed (Griffiths and Tauber, 1942). Nigam (1933) observed that o÷thecae were generally produced in summer, beginning in April and May, but very few during winter. At a temperature of 24.4 °C (76 °F) the average incubation period was 57.4 days, but at 30 °C (86 °F) it was 31.8 days.

Nymphal Instars. According to Gould and Deay (1940), it was difficult to determine the number of nymphal instars. Molting required only a few minutes, and the cast skin was usually eaten. From an examination of a large series of nymphs, they concluded that there were probably 13 instars.

The first-instar cockroach, immediately after hatching, consumes its castoff embryonic skin. It is white, then becomes grayish brown. It attains a length of 3.5 mm. In the early instars, the females have a median notch on the posterior margin of the ninth sternite, whereas in the males, this margin is either smooth or only slightly indented (Gould and Deay, 1940).

After the first instar, the succeeding instars are almost uniformly reddish brown, although the posterior margins of both thoracic and abdominal segments are of a darker color, giving the insects a transversely striped appearance (plate III, 8; figure 152). Wing pads are first noticeable in the third or fourth instar. These gradually become larger, and in the last nymphal instar they are about 7 mm long, distinct, and show venation. Prominent cerci and much smaller styli are present on nymphs of both sexes. In the next to the last instar, they may be hidden by the seventh sternite in females. As already stated, the styli are not present in adult females, and the presence or absence of styli is a convenient criterion for distinguishing males from females. In the final molt, the completely formed wings appear, requiring 25 to 30 minutes to expand completely. The cast skin is not eaten, although it has usually been eaten in all the preceding molts. Complete coloration requires 4 or 5 hours (Gould and Deay, 1940).

Habits. In southern California, the American cockroach is almost the only species found in the manholes and laterals of the sewer system, but it is seldom seen elsewhere - rarely in houses and apartments. Mallis (1969) estimated that in 177 apartments in 3 Texas cities, 99.7% of the cockroaches were Blattella germanica, 0.2% were - Periplaneta spp., and 0.1%, were Supella longipalpa. No Blatta orientalis were found in apartments. In North Carolina, 4 pest control servicemen made a survey in 3 cities to determine the percentage of apartments infested with the 4 principal domiciliary cockroach species among the infested buildings in housing projects in their regular monthly routes. They found B. germanica in 90% of the infested buildings, S. longipalpa in 9%, and P. americana in 1 % (Wright, 1965a). As in the Texas survey, no B. orientalis were found in multiple unit apartment buildings. However, when all types of buildings were surveyed, B. germanica accounted for 54% of the infestations and B. orientalis was second with 34%. Infestations of Periplaneta americana were found in 8% and of Supella longipalpa in 4% of the infested structures (Wright, 1965b). On a military base in North Carolina, percentages of the 4 species were: German, 84.9; American, 14.4; brownbanded, 0.5; and oriental, 0.2 (Wright and McDaniel, 1969).

The author has not been able to provoke American cockroaches to fly, merely by shaking them out of a maze. However, on a sunny day in July, at a temperature of 70 °F (21 °C) and relative humidity of 62%, some male and female American cockroaches were taken from rearing cans and thrown into the air to observe flight performance.' Some fluttered downward to ground positions, but others flew gradually upward, some so far that they were lost from sight. Along the Gulf Coast of Texas, American cockroaches have been observed to be common in palm trees and flying around street lights (Gould and Deay, 1940). In Needles, California, an extremely hot desert area, they are commonly seen flying outdoors, both day and night.

Mass Migrations. In common with Blattella germanica, Periplaneta americana sometimes engages in mass migrations. The former migrates by crawling (Howard, 1895; Marlatt, 1908; Guldin, 1967), but the American cockroach can migrate either by crawling or flying. Gould and Deay (1940) observed that during the summer, American cockroaches had migrated from store buildings for a distance of 4 blocks to some decaying maple trees in which they were infesting cavities. Another instance has been reported of these insects being found near an infested hospital, under the loose bark of large shade trees where they were feeding on exuding sap (Anonymous, 1967e). Migrations from restaurants and city dumps have also been observed (Gould and Deay, 1940). Both American and oriental cockroaches are known to be able to enter houses and apartments from sewers via the plumbing; control of cockroaches in sewers has decreased the infestations in near-by homes (Roth and Willis, 1957).

In experiments on the control of cockroaches with 10% DDT dust in houses, Stenburg (1947) found that the treatment was more effective against American than German cockroaches. He attributed this to the fact that American cockroaches traveled greater distances and thereby increased their chances of encountering the dust. He observed that German cockroaches appeared to move only short distances from their resting places, and apparently always returned to these harborages after searching for food and water.

Australian Cockroach, Periplaneta australasiae (F.) (Blattidae)

The Australian cockroach closely resembles P. americana in size and appearance and frequents similar habitats, but it cannot tolerate as much cold. This is indicated by its abundance in tropical areas and scarcity where the climate is as relatively mild as that of Southern California. The author has only rarely encountered the species in the hundreds of apartments and houses in which experiments have been made in the Los Angeles and San Francisco metropolitan areas. In the glasshouses of a large Los Angeles orchid nursery, it was abundant and was injuring the plants; this has likewise been the case in various other parts of the world where plants were grown in greenhouses. R. E. Wagner (personal communication) found P. australasiae in great numbers in the Florida Keys, in the damp areas between the trunks and old stubs of fronds of coconut palm trees.

Description. Measurements were made of widths (distance across wings at widest point when at rest) and lengths (distance between tip of head to tip of abdomen) for 25 males and 25 females of Australian and American cockroaches. These figures are shown in table 4, on the next page. Although there is but little difference between the 2 species in width, the male Australian cockroach is only 83% as long as the male American cockroach, and the female Australian species is 92% as long as her American counterpart. The basic reddish-brown color, and even the pattern of yellowish markings on the pronotum, are similar to those of the American cockroach. The markings (in the pronotum are more distinct, and in addition there is characteristically a lightyellow streak on the outer edge at the base of each forewing (plate III, 5). The ratio of females to males is about 1:1.

The early nymphal instars have a variable color pattern of predominantly brown, but with a narrow margin of black, as well as some light-yellow spots on the abdominal tergites. Later instars are basically reddish brown, but strikingly marked with light-yellow marginal spots on both thoracic and abdominal tergites (plate III, 8).

Life Cycle. In experiments made at 30░ C (86░ F), Willis et al. (1958) found the preoviposition period of the Australian cockroach to be 24 days. Between 20 and 30 o÷thecae were produced. The interval between successive o÷thecae was 9.8 days, the incubation period was 40.3 days, the number of eggs per o÷theca was 23.8, and the number hatched per o÷theca was 16.4, stated as averages. The percentage of hatched insects that matured was 55, compared with 84% for the American cockroach. Among nymphs reared alone, females had 11 or 12 instars, and the periods for nymphal development were 253 and 410 days, respectively. Males had 10 or 11 instars, and the developmental periods were 306 and 365 days, respectively. For females reared in groups, the period for nymphal development was 213 days, and for males-it was 198 days. Thus, nymphs reared in groups matured more rapidly than those reared alone.

Habits. In infested premises, P. australasiae occupies habitats similar to those occupied by P. americana (Cornwell, 1968). It is a pest of buildings in many areas of the tropics, but as just stated, in southern California the author has found it abundantly only in orchid glasshouses. The most common habitat in the glasshouses was in the space between small pots placed within the size larger pot to provide stability to small plants during watering. There is about 2 cm of space between the bottoms of the 2 pots, and this space is very damp. Australian cockroaches were found principally in these spaces, in large numbers.

The Australian cockroaches were feeding on orchid flowers and tender growth terminals. Although German cockroaches were feeding on these as well, the Australian cockroach is particularly known for its propensity for feeding on tender greenhouse plants. It has been reported to cause damage to plants in the tropical house of the Royal Botanic Gardens at Kew, England (Cornwell, 1968). In Denmark, P. australasiae occurred in large numbers in an indoor garden room of a Copenhagen restaurant, primarily in the plant beds, but sometimes it was seen by guests at tables. It had not yet spread to the kitchen or other parts of the restaurant, where the German cockroach was abundant. It was believed to have been introduced with plants from a greenhouse in the Netherlands (Anonymous, 11967e).

Brown Cockroach, Periplaneta brunnea Burmeister (Blattidae)

This species closely resembles the American cockroach in habits and appearance, but is more confined to the tropics in its geographic distribution. It is common in the southern and southeastern United States from the Carolinas to Florida and westward to eastern Texas (Edmunds, 1957). It has been collected indoors at points farther north, and in 1969 it was found in an apartment near Los Angeles, California, the first record of the insect in California (Reierson and Ebeling, 1970). The apartment was occupied by tenants who had arrived 4 months earlier from San Antonio, Texas, where the predominant species of Periplaneta is P. brunnea, according to Mallis (1969). It is also known that the brown cockroach is more common than the American cockroach in certain other areas of the South. Another accidental introduction of brown cockroaches from Texas was noted by Waldron and Hall (1972).

Despite the close resemblance of P. brunnea and P. americana, hybridization does not occur. A mixed colony of these 2 species plus P. fuliginosa was maintained for more than 3 years without the production of any recognizable hybrids (Eddleman and Simon, 1969).

Description of Adults. The adults are dark reddish brown (plate III, 6), resembling the American cockroach, but are somewhat darker in color. The 2 species also resemble each other in the yellowish margin of the pronotum. When measuring 25 individuals of each sex among those reared in our laboratory, the lengths and widths of Periplaneta americana, P. brunnea, and P. australasiae were recorded, and are shown in table 4. The data show that the American and brown cockroach are similar in length, but that the latter is the wider of the 2 species. The wings of the male brown cockroach do not extend beyond the tip of the abdomen as far as those of the American cockroach. Both the brown and the American cockroaches can be distinguished from the Australian cockroach by their slightly larger size and the absence of the yellowish streak on the outer edge of the base of each forewing that so distinctly characterizes P. australasiae.

The cercus of the American cockroach is stout basally, and tapers markedly toward the tip (Pratt, 1955). The sides of the last segment are more or less parallel, and 2 or more times as long as the basal width. The cercus of the brown cockroach is also stout, but the appendage is more evenly spindleshaped, with the last segment somewhat triangular and less than twice as long as its basal width. Periplaneta brunnea can fly, but its flight is usually of the gliding type.

Life Cycle. Judging only from the enormous production of P. brunnea in our rearing room at normal room temperature when compared with other species of Periplaneta, it appears to have an alarming reproductive potential. Possibly. there are ecological factors under actual field conditions that have thus far resulted in this species being generally less abundant than the American cockroach, even in the South.

Copulation occurred within a few hours after a female completed development, and egg deposition began 16 to 20 days later. It continued throughout her life. The periods between o÷theca depositions varied greatly, but could be as little as 5 to 6 days. Pope (1953) found that the maximum number of ovipositions was 30, but usually it was less. Edmunds (1957) kept some P. brunnea for 20 months, and they were still living and reproducing.

The O÷theca. While the o÷thecae of the American and Australian cockroaches are similar in appearance, those of the brown cockroach are strikingly different. Reierson and Ebeling (1970) found that the o÷thecae from a colony of brown cockroaches reared on Purina Dog Chow at 80 °F (27 °C) were 13.5 mm long (range 12 to 16 mm) and 5 mm wide at the widest point (range 4.5 to 5.5 mm). Those produced by Australian cockroaches reared under the same conditions averaged 10.9 mm long (range 10 to 11.5 mm), except for 1 o÷theca that was 13 mm long. Their average width was 4.4 mm (range 4 to 5 mm). The o÷thecae of American cockroaches averaged 8.3 mm in length (range 7.5 to 9.5 mm), and were about as wide as those of the brown cockroach. Thus, the o÷thecae of the brown cockroach averaged 2.6 mm longer than those of the Australian species, and 5.2 mm longer than those of the American cockroach.

Edmunds (1957), conducting all his experiments at 75 °F (24 °C), found that P. brunnea deposited the o÷theca from 20 to 24 hours after it was extruded. The number of eggs per o÷theca averaged 24 (range 21 to 28). Reierson and Ebeling (1970) obtained an average of 23.8 eggs per o÷theca at 80 °F (27 °C) and 65 to 75% relative humidity. The incubation period at this temperature was 35 days, compared with 61 to 63 days at 75 °in the Edmunds experiments.

The o÷thecae are at first brownish, but become black with increasing age, a characteristic of cockroach capsules. In large plastic rearing cans, the brown cockroach glues many of its eggs to the vertical interior walls of the cans or to the corrugated-paper mazes (Ebeling et al., 1966). In glass jars, the female frequently glues her o÷thecae to the jar lids. Under similar rearing conditions, the American cockroach glues her o÷thecae to the floor of the container. Both species at least partially cover their o÷thecae with bits of paper, cotton, or other available debris in an apparent instinct to hide them.

An interesting aspect of the biology of P. brunnea was brought to light by Willis et al. (1958), who found that eggs hatched from 91% of parthenogenetically produced o÷thecae and that 31.7% of the 208 hatched nymphs matured. All were females.

Maternal Care for Eggs. Cockroaches share with the somewhat related termites and earwigs the instinct of maternal care for their eggs. Edmunds (1957) described the phenomenon with respect to P. brunnea as follows:

In ovipositing, the female roach secreted from her mouthparts a frothy white substance which she seared over the spot in which she was going to deposit the egg capsule. Some females spent from 30 to 40 minutes preparing this frothy bed. The egg capsule was then deposited in the froth and covered with additional froth secreted by the female. Some cockroaches were observed spending, as much as 2 hours coating the egg capsule after it was deposited. The substance hardened to become a very strong cementing material. It was so strong that it was difficult to pry the capsule loose without causing it to rupture. For several hours after a capsule was deposited, the female rested with her body over the capsule and drove away any other roaches which approached.
It may be that if the o÷thecae of the brown cockroach were not guarded by the female, they would be in danger of being consumed by other cockroaches during the period when she customarily remains with them, since many are later found and eaten. Cockroaches that are injured or weakened in some way are also eaten by others. This may also be observed among other cockroach species.

Nymphal Instars. In the first-instar nymph, whereas the antennal segments of the American cockroach are uniformly brown, the first 8 and last 4 segments of the brown cockroach are white, and the intermediate ones are brown. The first instar nymph of the Australian cockroach resembles the brown cockroach in this respect. A median translucent area in the mesothorax of the brown cockroach nymph is absent in Perplaneta americana. The first 2 segments of the abdomen of the first-instar nymph of the American cockroach are entirely gray, brown, or reddish, while those of the brown cockroach have faint, cream colored spots on the dorsolateral margins. In later instars, these dorsolateral spots are extended to and include the sixth segment of the abdomen. The intermediate nymphal instars (plate III, 8) of the Australian cockroach are similar to those of the brown cockroach, except that the cream colored markings are more distinct, and extend throughout the length of the abdomen (Edmunds, 1957; Reierson and Ebeling, 1970).

Edmunds also observed that at 75 °F (24 °C), out of 25 newly emerged nymphs, the first male completed development in 263 days and the first female in 268 days, but that all nymphs had completed development in 277 days. The entire life cycle of the brown cockroach, from egg to egg, varied from 339 to 351 days - relatively brief when compared with the American cockroach.

Other Cockroach Species

Many people familiar with the common domiciliary species of the United States are not aware of the large number of other species, indigenous or accidentally introduced, that occur in this country. Some are at times abundant in certain regions. Excellent photographs of the species to be described here were presented by Roth and Willis (1960).

Pennsylvania Wood Cockroach, Parcoblatta pennsylvanica (De Geer) (Blattellidae)

This cockroach is indigenous to the United States, ranging through the midwestern, southern, and eastern states and north into Canada. Rau (1940) described it as "a trim, pretty creature, with its chestnut-brown color, and thorax and wing pads edged in white," but Hebard (1917) emphasized the variability of the species in different areas, and did not consider a general description of color to be of any value. The males are fully winged, and can occasionally be seen flying about outdoors. The wings of the females are short and nonfunctional. The males are considerably larger than the females, being 2.2 to 3 cm long compared with 1.3 to 2 cm for the females. Houses in rural districts and near wooded areas are commonly invaded, particularly by the males, which fly and are attracted to lights. This species is also frequently seen by motorists when driving through the woods at dusk (Gould and Deay, 1937,1940).

Parcoblatta pennsylvanica happens to have the widest distribution, but there are at least a dozen other species of the genus that occasionally find their way into houses in the United States, particularly P. lata (Brunner) and P. virginica (Brunner). Species of Parcoblatta are found throughout the country. They are generally seen in wooded areas, but one, P. desertae (Rehn and Hebard), is found only in desert and semidesert mountains of the Southwest (Rehn and Hebard, 1909; Hebard, 1917, 1942). Parcoblatta americana (Scudder) is the only species of the genus found in California. It is small, the males being 12 to 14 mm long and the females 9 to 13 mm. The females are wingless. The color is generally shining buff or brown, ranging to black in some females in the region of Mount Shasta, California. The smaller and paler specimens are found in the more arid and barren regions (Hebard, 1917).

Tawny Cockroach, Ectobius pallidus (Olivier) [=livens (Turton)] (Blattellidae)

This species may be found actively running about outdoors in temperate regions, such as southern England and parts of the European continent. It was first discovered in the United States in 1948 on Cape Cod, and has become established in southeastern Massachusetts. It is common in some areas (Gurney, 1953; Smith and Chao, 1956). It does not attack household foods or goods, but could become a nuisance when attracted to dwellings by lights. This is a pale-brown cockroach, smaller than Blattella germanica and lacking the dark lines on the pronotum that characterize the latter. The wings have many tiny, dark spots that can be seen only with the aid of a hand lens. The nymphs are also pale brown (Smith and Chao, 1956).

Smoky Brown Cockroach, Periplaneta fuliginosa (Serville) (Blattidae)

This species is uniformly shining brownish black or mahogany in color. Both sexes have wings that extend beyond the tip of the abdomen. It is common in the southern states from central Texas eastward, and has been found in heated buildings in isolated locations as far north as Iowa, Indiana, and Illinois. This is the only uniformly dark-colored species of Periplaneta in North America, and is also the only species not known to occur in other parts of the world (Hebard, 1917). It flies to lights at night, and is sometimes attracted to lighted porches. It has been recorded as second only to the German cockroach as a pest in houses in southwest Georgia (Haines and Palmer, 1955), but is more commonly found in garages, outbuildings, and woodpiles. It is sometimes a pest in greenhouses (Hebard, 1917; Gould and Deay, 1940; Cornwell, 1968).

Woods Cockroach, Eurycotis floridana (Walker) (Blattidae)

This species occurs in the West Indies and southern Florida, where it may be found in almost any outdoor sheltered location - under the bark of dead pine stumps and logs, in tree cavities, under palmetto leaves on the ground, under debris in leaf mold or decaying wood, in stacked lumber and firewood, and often in cavities in limestone rock (Hebard, 1917; Roth and Willis, 1960). It may occasionally be found in houses (Creighton, 1943, 1954). Eurycotis floridana is 4 to 4.5 cm long. Adults and nymphs are rich redbrown to almost black, but the nota (dorsal thoracic segments) of the late nymphal instars are often conspicuously marked with broad bands of pale yellow. The tegmina (thickened forewings) of both sexes are very short, extending barely beyond the posterior margin of the mesonotum, and the hindwings are lacking. When alarmed, the adults of both sexes emit a greasy liquid with a most repellent odor (Hebard, 1917; Eisener et al., 1959). A single gland on the underside of the abdomen ejects a spray of it toward the rear.

Harlequin Cockroach, Neostylopyga rhombifolia (Stoll) (Blattidae)

This cockroach, believed to have originated in Indo-Malaysia (Roth and Willis, 1960), has become established in various parts of the Western Hemisphere, including Mexico. From Mexico, it migrated northward to Nogales, Arizona (just across the border), and it also occurs in Baja California (Hebard, 1917). In California, a single adult was found in a warehouse in Los Angeles in 1958, and another in a box of tomatoes in a market in Santa Rosa in 1965. An adult was found on a tomato fruit in a field near Watsonville in 1966. This species was occasionally found on Travis Air Force Base, California, where cargo planes were arriving from Vietnam during the war (George Buxton, personal communication). The length varies from 2 to 2.7 cm. The tegmina (forewings) of both sexes are small lobes, only about 4 mm long, and hindwings are entirely lacking. The basic color is shining brownish black, marbled with yellowish buff in a distinctive pattern that makes identification easy.

Surinam Cockroach, Pycnoscelus surinamensis (L.) (Blaberidae)

This species is distributed throughout the world in the humid tropics and subtropics. In the United States, it is abundant in the Florida peninsula and in the Brownsville area of Texas, but it is also established in New Orleans, San Antonio, and Hawaii. The Surinam cockroach is 2 to 2.5 cm long, and is shining brown to black. In both sexes, the wings extend beyond the tip of the abdomen. The rear margin of the adult's prothorax is sinuate (curving in and out), and the front margin is marked by a pale band in some specimens.

Where the climate is favorable, the Surinam cockroach is generally found outdoors under rocks and boards, under litter, or in damp soils. In Hawaii, it has been found in soil around the roots of pineapple, under mulching paper, or even feeding on pineapple roots (Illingworth, 1927, 1929). In colder regions, this species can sometimes be found in greenhouses, where it can cause damage to plants. In some Philadelphia greenhouses, Surinam cockroaches were present "by the millions." From 30 to 50 thousand rose plants out of 200 thousand were so severely injured by the gnawing off of the bark, young buds, and shoots of the main stems that they had to be discarded (Doucette and Smith, 1926). In a greenhouse in Germany, many of these cockroaches penetrated soil to a depth of 8 to 10 cm, and a few even more deeply. Some insects spent several days at a time in chambers at the bottoms of the holes. Nymphs molted and females produced their young in such chambers (Roeser, 1940). Pycnoscelus surinamensis is parthenogenetic in North America and Europe, and the offspring are all females, but it is bisexual in Indo-Malaysia (Roth and Willis, 1956).

Madeira Cockroach, Leucophaea maderae (F.) (Blaberidae)

This species is probably native to West Africa, but was first described from the island of Madeira. It occurs in the western Mediterranean area, in many parts of South America, throughout the West Indies, the Bahama Islands, Hawaii, and in a Puerto Rican section of New York City. Nymphs were reported by quarantine officials to be inhabiting a residence on Cheli Air Force Base, Maywood, California, in November, 1972. The adults are pale brown to tawny olive in color, and 4 to 5 cm long - about 7 mm longer than our largest common species, Periplaneta americana. The wings of both sexes reach the tip of the abdomen. The forewings are marked with 2 dark-brown lines in the basal area, and the posterior areas are mottled. The nymphs have very small, short spines that are particularly noticeable along the dorsal posterior margin of each segment. The adults crawl about slowly but fly actively, and like Eurycotis floridana, give off an offensive odor when disturbed (Cornwell, 1968). The Madeira cockroach has a very long life span, reported to be 2.5 years by Scharrer (1951), who recommended this large insect as a convenient and useful laboratory - animal. He stated that experimental operations on it might be significant with respect to mammals, and the species has, in fact, become popular in many research laboratories for this reason.

The Madeira cockroach is frequently intercepted in quarantine at seaports, which is understandable in view of its predilection for fruit, particularly bananas (Sein, 1923). Despite the high temperature requirements of this species, it can adapt itself to sheltered life in temperate climates, as shown by its establishment in New York City in buildings having sufficiently high temperatures. There appears to be no reason why it could not become more widely distributed. The brownbanded cockroach also requires relatively high temperatures, but has nevertheless become widely distributed throughout the United States (Gurney, 1953).

Lobster Cockroach, Nauphoaeta cinerea (Olivier) (Blaberidae)

This insect has world-wide distribution in tropical areas, where it is known as a domiciliary species. It was first recorded in the southern United States in 1952, and also occurs in Hawaii, where it is known to kill and eat the Pacific beetle cockroach, Diploptera punctata (Eschscholtz) (Illingworth, 1942). The lobster cockroach, so named because of the lobsterlike design on its pronotum, is ashy gray in color and 2.5 to 3 cm long. The wings do not cover the abdomen, although they are slightly longer in the male than in the female.

Blaberus craniifer Burmeister (Blaberidae)

This large, broad cockroach is known from Mexico and Central America, but in the United States it has become established only in Key West, Florida (Hebard, 1917). However, cultures may sometimes be seen in zoological laboratories. It is said to be abundant in houses in Cuba. The normal habitat is under rotting logs and vegetation in rain forests. Hebard found the length of the male's body to be (rounded figures) about 4.3 to 5 cm; the width of the pronotum, 2 to 2.2 cm; and the length of the tegmina (forewings), 5 to 5.5 cm. The latter extend beyond the tip of the abdomen, about as shown by the foregoing figures. The corresponding figures for the female were about 5.5 to 6 cm, 2.1 to 2.3 cm, and 5.4 to 5.8 cm, respectively. The general body color is blackish brown, with an even darker area on the pronotum of the adult that bears pale markings that suggest the human eyes, nose, and mouth. The same area on the nymph bears 4 pale spots, and the abdomen has a median double row and lateral double rows of pale spots. In the related Blaberus atropos (Stoll), indigenous to South America, the fancied "death's-head" marking is on the mesonotum and metanotum (Hebard, 1917; Roth and Willis, 1960). The adults of B. craniifer are long-lived, the males averaging 14 months and the females, 16 months.

Cryptocercus punctulatus Scudder
(Cryptocercidae)

This primitive, wingless, wood-eating cockroach is discussed here only because of its great scientific interest. The males and females are of the same size and appearance; 2.3 to 3 cm long; wings are completely lacking; the general color is almost black, tinged brown; the eyes are very small; the pronotum is very convex, except for a wide and deep mediolongitudinal depression, and has a broad margin that is raised above the head, thought to give the head protection while burrowing. This species occurs in the United States in heavily forested areas of the Pacific Coast, and in the Appalachian Mountains from Pennsylvania to northern Georgia. Hebard (1917) described a typical habitat in fir logs in Oregon. The insects were found only where the wood was soggy and the bark could be easily removed. The cockroaches had eaten their way through the sapwood, preferring the places where it was soft, soggy, and decayed. This species is found in hardwood as well as softwood material. The infested wood is generally "soft, punky, and wet," but Cleveland et al. (1934) also found C. punctulatus in sound logs that had been down for only a few years.

This cockroach is of great interest because of the presence in its alimentary canal of cellulose digesting, flagellated protozoa, transferred from older insects to the young as in the termites, which are believed to be descended from the cockroaches. The first fecal pellets passed by the older nymphs after a molt contain large numbers of encysted protozoa. When eaten by the newly hatched nymphs, these cysts ensure a heavy population of flagellates within a few days. Cryptocercus depends on these flagellates for the digestion of cellulose.

One genus of flagellates (Barbanympha) contained the largest and most abundant species found by Cleveland et al. (1934) in every one of the thousands of Cryptocercus they examined. They contained the enzymes cellulase and cellobiase, which the cockroach itself was unable to produce, and these enzymes converted cellulose into soluble sugar (dextrose) (Trager, 1932). Cryptocercus possesses 2 genera of protozoan symbionts (Trichonympha and Leptospironympha) that are also present in termites (Honigberg, 1970). Transfaunations can be achieved between Cryptocercus and Zootermopsis by feeding one the intestinal contents of the other (Cleveland et al., 1934; Nutting, 1956).

Control of Cockroaches

Good Housekeeping. Cockroaches cannot live in human habitations without the food and water they provide. Obviously, good housekeeping is an important factor in control. Food particles should not be allowed to remain on shelves or floors. Dishes should not be left unwashed after a meal, particularly overnight. Areas under refrigerators, stoves, sinks, and furniture should be checked to see whether food has accidentally fallen or has been swept into them or dropped there by children or pets. If pets are fed indoors, food particles should not be left in their dishes after feeding, particularly not overnight. Keep cereals, crackers, meats, vegetables, flour, pet foods, and all other foods covered or in a refrigerator at all times between uses. Keep garbage and waste containers covered, or empty them into a covered container every night.

Water is often available as condensation or spillage under the refrigerator. Patches of water often remain for hours in certain locations after a floor mopping or following the use of a washing machine. Other common sources of water for cockroaches are the traps of sinks, washbasins, tubs' and toilet bowls; flush tanks; condensation on cold pipes and windows; leaking pipes and faucets; miscellaneous water-filled containers such as pets' drinking dishes, aquaria, vases, empty beverage bottles; and the juices from soft fruits and vegetables (Roth and Willis, 1960).

Cockroach infestation is favored by a cluttered household. Stored magazines and newspapers, corrugated-paper boxes and piles of paper bags should be eliminated. They not only provide harborage and breeding areas for cockroaches, but also provide areas into which the cockroaches can escape from insecticide residues when control is attempted. Insecticides are repellent to cockroaches in varying degrees.

Application of Insecticides. If liquid sprays are to be applied, and ideally for dusts also, all shelves and drawers should be emptied and cleaned. After treatment, shelf paper may be placed on sprayed areas and on dust deposits. If a relatively safe dust such as boric acid is to be used, it is recommended that the operator reach carefully behind shelf contents and apply the dust with a bellows powder blower ("Getz Gun"), bulb duster, or plastic squeeze bottle (figure 29, chapter 3) in a narrow band along intersections and into corners and crevices. Shelf paper lifted while the powder is applied may then be allowed to fall back into place.

When applying insecticides for cockroach control, pest control operators ordinarily ask the occupants of the treated premises to remove cooking and eating utensils and foodstuffs when there is danger of their becoming contaminated with insecticide. For example, they may be placed on a table in the center of a room and covered with a sheet. Occupants are asked to leave the building and remove their pets during treatment.

Treatment for cockroaches, like so much of household pest control, is "spot treatment." The insecticide is applied to relatively limited areas where cockroaches are likely to hide during the day or where they are likely to travel at night. Most cockroaches congregate in dark, warm. damp places, such as under and behind the refrigerator and stove and under the sink, particularly the "dead space" between the sink and the wall. The most thorough treatment can be made under the refrigerator and stove if the kick panels are first removed, allowing the person applying the spray or dust to see what he is doing. Many cockroaches seek harborage and breed in the insulation in the walls of a refrigerator, stove, or range. These insects should come in contact with insecticide residues when they come out to forage for food and water. Insecticide sprays should also be applied behind window and door frames, under and behind furniture standing against the wall, on the undersides of tables and chairs, on closet and bookcase shelves, and in cracks and apertures around cabinets. Cockroaches are attracted to warmth, and may hide under and behind radiators and water heaters or in television sets and radios. Apply enough spray to wet surfaces thoroughly, but not enough to drip or run. If both sprays and dust are to be used, spray first and apply the dust after the spray dries, forcing the dust into cracks and voids.

When cockroaches are abundant, they are likely to be located in wall voids. In apartment houses, they may migrate from heavily infested to lightly infested or uninfested apartments via these voids. After blowing an insecticide dust into openings around utility pipes or any other openings into walls, particularly in kitchen and bathroom areas, such openings should be sealed to prevent further ingress or egress of the insects. Holes through which to dust wall voids can be drilled through plaster if necessary, and the holes can then be filled with matching plaster. Holes can also be drilled at the top of the kick panel under a kitchen cabinet, or in the floor of the cabinet, in order to dust the subcabinet voids, unless the latter can be reached by removal of drawers or through existing cracks or apertures. After treatment, seal all cracks and crevices where cockroaches may hide. Even very narrow cracks may harbor the small nymphs. If the backsplash behind the sink and on the sink cabinet has parted from the wall, leaving a narrow aperture, this is a particularly favored harborage for cockroaches and should be sealed.

Insecticides

Because the German cockroach is almost universally resistant to chlorinated hydrocarbons, the organophosphorus and carbamate insecticides are now used for control of this species. Suggested insecticides and dosages are: diazinon, 0.5% spray or 10% dust; propoxur (Baygon's), 1% spray or 2% bait; chlorpyrifos (Dursban's), 0.50/,) spray or 1 % dust; dichlorvos, 0.5% spray or 1 % bait; malathion, 5% spray or dust; and Kepone«, 0.125% bait. It has been our experience that the reduction in German cockroach infestation from sprays with base-oil solutions or emulsions of the insecticides currently being used against German cockroaches in multistoried apartment buildings can be expected to average around 85%, based on the number of cockroaches trapped before and a month after treatment. This is also approximately the average degree of control accomplished by pest control operators. On the other hand, Burden et al. (1972), applying 0.5% chlorpyrifos emulsion spray in ground-level homes constructed of concrete blocks, were able to obtain German cockroach reductions that were "95% within 1 day, 97% within 2 weeks post-treatment, 99% from the third through the eleventh week, and averaged 98% at 12 weeks post-treatment." Wright and Hillmann (1973) applied 4 treatments: 1 % chlorpyrifos dust, 0.5% chlorpyrifos spray, 0.5% chlorpyrifos spray plus 1 % chlorpyrifos dust, and boric acid powder, then spot-treated at the 2-week and 1-month recheck periods wherever necessary, mostly in harborages missed during initial inspection and treatment. They used approximately 22% as much material in the retreatments as in the initial treatment, and did not use disproportionate amounts in the different treatments. They obtained controls ranging from 97 to 100% for as long as 6 months following the initial treatment.

Pyrethrin aerosols are commonly used to flush cockroaches from their daytime hiding places for pre- or post-treatment estimates of infestation levels in buildings, or to drive the insects from their hiding places so as to facilitate treatment with residual insecticides. Pyrethrins and their synergists are also added to insecticide solutions or emulsions for more rapid knockdown or presumed increase in the efficacy of the sprays. In field tests in which pyrethrins plus synergists were added to 3 insecticide solutions, 1 emulsion, and to boric acid powder, the pyrethrins resulted in more rapid knockdown, but evaluations made a month after treatment did not reveal, on the average, any increased insecticidal efficacy (Ebeling and Reierson, 1973a). In addition, when pyrethrins were used in apartment buildings they had the disadvantage of driving cockroaches from the treated apartment to adjacent untreated apartments via the wall voids.

Pyrethrin formulations, particularly dusts, frequently cause allergic reactions in people with such allergic tendencies as hay fever and asthma. Some persons applying certain organophosphorus insecticides suffer respiratory disorders, but the carbamate propoxur has not been reported to have this disadvantage (Lisella, 1973).

Resmethrin is a synthetic pyrethroid that has been suggested as being much less irritating to the throat than pyrethrins. Resmethrin does not seem to flush cockroaches out of their hiding places as quickly as pyrethrins, and the insects appear to be less agitated. However, within 15 to 20 minutes, a greater proportion of the cockroach population is said to be flushed out, providing a more accurate estimate of the infestation level (Grothaus et al., 1972).

If base oil (deodorized kerosene) is used as a carrier in the spray, it should not be applied near a flame, as under a gas-operated water heater; a water-base spray (emulsion) should be substituted in areas of fire hazard. Ideally, base-oil solution should not be applied to plaster, asphalt tile, or linoleum, for it leaves an oily stain on plaster, destroys the waxy finish on tile or linoleum, and leaves a slippery surface that may be hazardous to occupants of the sprayed building. Base oil sometimes penetrates between old floor tiles and weakens their bonding to the floor. In cockroach control, it is necessary to spray beneath and behind the refrigerator and stove and along baseboards, and thereby get base oil on the floor at least in these out-of-sight areas. An experienced serviceman sometimes sprays with base-oil solution along baseboards in other areas when the floor is covered with tile or linoleum, but he sprays very lightly. Most disadvantages of base oil can be avoided by using water as the carrier. However, water emulsions have their disadvantages also. They tend to leave visible residue ("spots") when the emulsion dries. Either base oil or water will leave unsightly residues if applied over greasy or dirty surfaces to the point of runoff, for this may cause streaks to form around the treated area.

The residual efficacy of insecticides applied in liquid sprays is greatly affected by the nature of the treated surface, as shown in table 5. Dust deposits are less affected by the substrate, and this is one of the advantages of dust formulations.

Dusts can be applied most effectively in cracks, crevices, and enclosed spaces such as wall voids, voids under cabinets, and voids under built-in appliances. In visible places, such as along baseboards and moldings and in bathrooms, dust deposits are unsightly and liquid sprays are more appropriate. In the bathroom, there are few places where dusts are not unsightly, but if they are blown into the louvers or razor-blade slots of medicine cabinets, they can be widely distributed in a wall void that is likely to harbor cockroaches. The best results are obtained with both spray and dust, each in appropriate locations. A spray or dust treatment, or a combination of the two, can be effectively supplemented with cockroach bait that may be placed in out-of-sight areas similar to those in which a dust would be applied. Dichlorvos bait initially kills cockroaches more rapidly and completely than Baygon or Kepone, but the latter provide longer residual control. Glycerol has been found to be effective as a feeding stimulant in poison baits, and is much more so than maltose, the most effective of the sugars (Tsuji and Ono, 1970b).

Vapors and Gases in Enclosed Spaces

A piece of dichlorvos resin strip 1 sq in. -(2.5 cm) in area, attached to the underside,of the lid of a 24-gal (91-L) garbage can, results in complete mortality of all active stages of any of the 4 principal species of cockroaches in 24 hours under room-temperature conditions (Ebeling, 1964b). A "ministrip" (2 x 2.5 x 0.25 in.; 5 x 6.5 x 0.7 cm) is now available that has an adhesive substance on one side so that it can be pressed against the bottom of a garbage-can lid. The ministrip, placed in closed kitchen sink cabinets in apartments infested with German cockroaches, resulted in 75 to 90%, mortality during the first 7 to 12 weeks, decreasing to 50% mortality at the end of 12 weeks. The results with the ministrip were not significantly different from those with a spray of 1.5% malathion plus 0.5% diazinon (Wright, 197 I).

The efficacy of resin strips depends on the concentration of dichlorvos vapor they can generate in the area to be treated. In a normally ventilated room, the concentration does not reach a sufficiently high level for cockroach control, but the strips are effective against them in enclosed spaces with very poor ventilation or none.

As indicated by the experiments of Barnhart (1963) and Cantwell et al. (1973), dry ice can be used as a safe and inexpensive means of generating a gas for exterminating cockroaches in food service carts, as used, for example, in hospitals. These carts have many areas where cockroaches can hide and be inaccessible to sprays or dusts. Tompkins and Cantwell (1973) developed a dosage and time schedule for killing not only active stages, but also the eggs. The cart was centered on a 12 x 20-ft (3.7 x 6.1-m) sheet of black 6-mil plastic. Twenty pounds (9 kg) of dry ice was broken into pieces of appropriate size for placing at different levels in the cart. The plastic sheet was then drawn up and tied at the top. The volume of the enclosed cart was 71 cu ft (2 cu m). The level of carbon dioxide was monitored with a Gow-Mac Gas Analyzer at 5 and 24 hours. At 78 °F (26 °C), the minimum concentration of carbon dioxide required for the 24-hour period of the test was 21% in order to kill not only all the female German cockroaches with attached o÷thecae that were used as the test insects, but also to prevent hatching of their eggs over the 30-day period of observation. This method of fumigation has the advantage of being safe and not requiring special training of personnel.

Boric Acid for Cockroach Control

Experiments made in our entomology laboratory at UCLA showed that the principal factor affecting the effectiveness of an insecticide against cockroaches was its repellency (Ebeling et al., 1966). The greater the repellency of the insecticide, the greater the chances that a certain percentage of cockroaches would learn to avoid treated areas before picking up lethal doses. Cockroach control is ordinarily accomplished by "spot treatment" of the dark and hidden places normally frequented by cockroaches during daylight hours. Some of the surviving insects in these areas may learn to avoid the treated areas and seek harborage elsewhere in the building. In apartment buildings, some cockroaches may leave treated apartments, and may invade untreated apartments via the wall voids or hallways.

Boric acid powder is the least repellent of the insecticides tested. In buildings treated with boric acid, cockroaches will crawl over the deposits repeatedly. Although they do not die as rapidly as when treated with more toxic insecticides, few if any should be seen after a week or 10 days. Boric acid is inorganic, and in an area in which it can remain dry and is not likely to be removed, it will continue to kill cockroaches indefinitely (Ebeling et al., 1966, 1967, 1968; Moore, 1971, 1972). Before using, it must be passed through a sieve or screen to break up lumps and facilitate its passage through the usual dust applicators.

Sodium fluoride is likewise an inorganic powder, and is much more toxic to insects and to humans than boric acid, but it is highly repellent, and has been far less effective in control of cockroaches, both in laboratory devices utilized to simulate typical harborage areas in buildings (choice boxes, mockup wall voids, mockup closets) (Ebeling et al., 1967) and in experiments made in apartment buildings (Ebeling et al., 1968). As applied for cockroaches, boric acid is also effective for control of silverfish.

Boric acid acts in part as a contact insecticide, penetrating through,the insect's cuticle. In addition, cockroaches remove the dust from their antennae and legs while passing these appendages through their mouthparts. In this way, much dust is consumed, and boric acid, like sodium fluoride, acts partly as a stomach poison. Figure 153 shows the point to which boric acid, stained with Janus Green dye, generally penetrates into the alimentary canal of an adult German cockroach within 3 hours when the insect is placed on a deposit of 2 cc of boric acid in a petri dish. Repeated trials showed that the powder always filled the crop of a cockroach to capacity within this period, and although the insect might continue to preen for another 2 hours, its esophagus, pharynx, and mouth were packed with powder and no more could be ingested. The powder in the crop is prevented from moving farther into the alimentary canal, except in very small quantities, by the denticles of the armarium of the proventriculus.

In areas in which a dust would not ordinarily be applied, the liquid insecticides discussed earlier can be employed advantageously for a liquid - dust combination treatment. Gupta et al. (1973), experimenting with 0.5% chlorpyrifos spray alone or in combination with 2% propoxur bait, 2% diazinon dust, boric acid, or Drione« (silica aerogel plus pyrethrins), found that, in apartments with bad sanitation, only where dusts were used was control of German cockroaches satisfactory 2 months after treatment. They recommended the use of "a combination of inorganic dusts and insecticidal sprays (with knockdown qualities) that can be applied in appropriate and somewhat mutually exclusive areas, so that the efficacy of both the formulations is fully realized." When boric acid alone is used as the residual insecticide, pyrethrin aerosols can be applied in areas of heaviest cockroach concentration to hasten control of the insects. Aerosol canisters, such as shown in figure 20, chapter 3, are suitable for this purpose, but have the disadvantage of not being refillable. A refillable aerosol generator with a flexible hose, such as the Hi-Fog (figure 21, chapter 3), can be used just as effectively and also more economically in extensive treatments. The cockroaches should then be swept up and destroyed as soon as possible after treatment, otherwise many may recover. Boric acid dust should then be applied in the usual way. The efficacy of the pyrethrin-boric acid treatment, as determined in extensive field experiments in California (Ebeling et al., 1968), was later confirmed in other field experiments (Moore, 1971, 1972).

Japanese entomologists found that 20% boric acid, in starch-bait tablets or granules, was not repellent to German cockroaches. The addition of 0.5% lindane or fenitrothion resulted in an increased initial rate of mortality, but because of their repellency, these insecticides also increased the period required for a 100% kill. Methyl myristate at 0.02 to 0.2% or maltose at 10 to 15% concentration increased the amount of bait consumed. With a given amount of bait, small granules scattered widely were more effective than the larger tablets not so widely distributed (Tsuji and Ono, 1970a). Another advantage would be that granules are less likely to be found and consumed by small children and pets.

Application of Boric Acid During Construction. As an inorganic dust, boric acid lends itself well to "insectproofing" at the time of construction. The dust is applied in enclosed spaces, such as attics, dropped ceilings, wall voids, voids under cabinets, and built-in appliances such as ranges and refrigerators. Half-inch (12-mm) holes can then be drilled into wall voids and subcabinet voids to facilitate the application of the dust. The treated areas are not only eliminated as harborage and breeding places for cockroaches but, with the relatively nonrepellent boric acid dust, they act as traps to eliminate cockroaches that may develop in untreated areas of the building. A water-type fire-extinguisher (figure 33, chapter 3) is particularly effective for this kind of dust application. Although cockroaches can still gain entry and develop in the "living space" of a building, they will never become so abundant as they would have if boric acid had not been applied in enclosed and inaccessible areas of the building at the time of construction (Ebeling, 1969).

Toxicity of Boric Acid to Humans. Boric acid has long been used in medications, and although in recent years such use has been greatly diminished, there is much confusion as to its potential hazard when used as an insecticide. Its LD50 is relatively high [3,200 and 3,500 mg/kg in male rats and 4,100 mg/kg in female rats (Weir and Fisher, 1972)], but it should be borne in mind that boric acid is used undiluted or only slightly diluted as an insecticide, whereas most insecticides are used only in greatly diluted form. Nevertheless, there appears to be a considerable margin of safety in the use of boric acid. Absorption of the material in unbroken skin is negligible (Pfeiffer, 1951). A standard teaspoonful of boric acid, screened to break up lumps, weighs 2.2 grams. Sublethal doses (e.g., 3 g) are rapidly excreted in the urine (Chittenden and Gies, 1898; Wiley, 1907). When 2 normal women were given approximately 2 grams of boric acid during the third, fourth, and fifth days of a 28-d. metabolism experiment, 93 to 94% of the boron was recovered during the first week, demonstrating its rapid absorption and metabolism (Kent and McCance, 1941). Chronic intoxication has occurred in man after daily ingestion of 4 to 5 grams of boric acid for 3 to 4 weeks and 6 to 20 grams of borax for as long as several months. On the other hand, death has occurred in adults within 46 hours after oral ingestion of as little as 7.5 grams and within 46 hours after the oral ingestion of 15 grams. Although infants have survived doses of 4.5 to 9 grams of boric acid in several hospital accidents, death to newborn babies has resulted from accidental administration of 3 to 13 grams (Pfeiffer, 1951). These figures show that death from boric acid is likely to occur only from accidental ingestion of considerable quantities. As in the case of any insecticide, as well as many common household powders and liquids, containers should be conspicuously labeled and kept out of reach of small children.

Control in Sewer Systems

In the warmer areas of the United States, cockroaches inhabit the sewer systems of many cities, sometimes in enormous numbers (Eads et al., 1954; Schoof and Siverly, 1954; Roth and Willis, 1957; Wagner et al., 1966; Anonymous, 1968a; Mackie, 1969). There is some danger of cockroaches moving from sewers to buildings, particularly if sewage backs up into manholes, forcing the insects to flee (Mackie, 1969). The species most commonly involved is the American cockroach, although the oriental cockroach has occasionally been found in large numbers. On the other hand, the oriental cockroach is commonly found in the water-meter vaults in alleys and parkways, while the American cockroach is never found in them.

Good control of the American cockroach in sewer manholes was obtained by blowing Drione«, a silica aerogel-pyrethrin formulation, into the manholes at the rate of 0.3 lb (135 g) per manhole. The dust was applied with gasoline powered centrifugal blower (figure 154) of 500 to 1,500 cfm (14 to 42 cu m per minute) capacity. Even with this small quantity, dust was seen rising from plumbing vents protruding from the roofs of houses on both sides of the street and from manholes up to a block away, indicating good penetration of all sewer-system laterals (Wagner et al., 1966). The same insecticide and procedure were used to control cockroaches in Yakima, Washington (Anonymous, 1969a). As in the treatments noted by Wagner, no live ccokroaches were found immediately after treatment, but 2 miles away the sewage-disposal system was flooded with the insects that had been washed from the treated sewer manholes and laterals. Periodic inspections showed little reinfestation over a 2-year period, but additional infested areas found during routine sewer-maintenance work were treated in the same manner, and this method continues to be used. Other cities in the Pacific Northwest have adopted the same treatment.

In Phoenix, Arizona, good results were obtained when carbaryl (Sevin«) insecticide dust was blown into manholes, using a portable crop duster that gave the dust a 36,000-volt electrical charge as it left the blower spout (Anonymous, 1968a).

Application of a 50% chlordane emulsion in sewer-system manholes for, American cockroaches and in meter boxes for oriental cockroaches was also found to result in good control in San Diego, California. Even the spraying of only the upper 3 ft (1 m) of the manhole was successful in controlling American cockroaches in one experiment. The control campaign involved the treatment of 14,500 manholes at a cost of 22 cents each and 150,000 water-meter vaults at 4.5 cents each, including the cost of materials, labor, and equipment (Mackie, 1969).


FLIES


Fly Species List

Flies belong to the large and important order Diptera. Stone et al. (1965) listed 1,971, genera and 16,130 species of flies occurring in America north of Mexico. Among the flies are some of man's greatest tormentors and some of the most important species from the public health standpoint.

All winged flies have only 1 pair of wings, the hind pair being replaced by a pair of clubshaped organs (halteres) used for balancing (figure 65, chapter 4). There are about 384 species of flies that are wingless or have only rudimentary wings (Cole. 1969b). Further information on the morphology of adult as well as immature stages of flies, and a discussion of the 3 major taxonomic groups (suborders), may be found in chapter 4. In the present chapter, only synanthropic species, also known as "domestic" or "filth" flies, will be discussed - species that either require man's environment or are greatly benefited by it. There are about 200 such species (Greenberg, 1965), so only the more important are included here. Other Diptera (mosquitoes, gnats, midges, etc.) are discussed in chapter 9.

Except for the psychodids, the flies discussed in this chapter are in the suborder Cyclorrhapha (see near the end of chapter 4), in which all species lack mandibles and most species have no maxillary blades, although the maxillary palpi are retained. Among the nonbiting species, are the house fly, the blow flies, flesh flies, eye gnats, and Drosophila flies. The labial labella (figure 46, chapter 4) of these flies are large, soft, oval lobes that can be spread out to form a broad disk by which food can be collected and conveyed to the food canal of the haustellum. The Cyclorrhapha, despite having no specialized piercing mechanism, includes some species, the horn flies and stable flies, that can bite and pierce. The labium forms the piercing organ (figure 46, F and G), and the labella, instead of being soft, spreading lobes, are a pair of small, hard plates at the tip of the theca, and bear eversible teeth internally (Snodgrass, 1944).

In the United States, the house fly is still generally the most abundant species in houses, especially in the southern states, but other flies that resemble it, such as the little house fly (Fannia canicularis), can also be troublesome, mostly as "doorway pests." The face fly (Musca autumnalis) and the cluster fly (Pollenia rudis) are often more abundant than the house fly in houses in some areas, especially the midwestern states (Osmun and Butts, 1966). Face flies are usually house pests only in the overwintering form. Resistance of house flies to various organochlorine and even to some organophosphorus compounds should result in their retaining considerable importance as household pests. One or two treatments per year are not likely to result in control, as they did in former years.

The Influence of Modern Livestock Production Methods on Fly Production and Fly Control

According to Anderson (1966a), the "filth fly" problem is continuously increasing in magnitude, because:
(1) There is an increased number of poultry and other livestock; (2) the economics of shipping and marketing influence the location of livestock concentrations near metropolitan consumer centers; (3).man's rapidly expanding suburban populations are bringing more people into closer proximity and daily contact with previously relatively isolated rural communities; and (4) recent changes in agricultural technology economically favor large concentrations of animals.
The result is that in the fringes of large urban areas, we are developing high-density, low-area monoculture of beef and milk cattle, poultry, etc. These, like monocultures of plant crops, tend to create difficult pest problems. Monoculture is the cultivation of a single product over an extensive area to the exclusion of other possible uses of the land. This practice decreases the complexity of the ecosystem, and this is generally disadvantageous to the natural enemies of livestock or plant-crop pests.

Before the current practice of high concentration of livestock in limited areas, the animals scattered their feces in small piles over large ranges or pastures. This created a favorable ecosystem for minimal fly development. Poultry and hogs could consume various pest arthropods that developed in their feces, but this is no longer possible. In cattle feedlots, all important predators associated with pasture feces have been eliminated, along with almost all coprophagous arthropods that efficiently convert pasture feces into arthropod life (Anderson, 1966a). The importance of the latter factor is indicated by the estimates quoted by Anderson of the annual production of manure in the United States - nearly 2 billion tons per year by cattle alone. Sound management in manure disposal is essential for effective fly control programs. A complete utilization of manures as fertilizers would appear to be a worthy goal toward which to work, and consistent with the current desire for "recycling" and efficient utilization of our resources.

Pictorial Key for Recognition of Species

There are many species of flies that are similar to the house fly in size and general appearance. The Pictorial Key to Common Domestic Flies in the United States (figure 155), prepared by the Center for Disease Control of the United States Department of Public Health, is useful in helping to distinguish the adults of these flies, as well as to distinguish species in other groups that are easily separated from the species resembling house flies by conspicuous differences in size and/or color, but which should be distinguished from one another. A paper written by Dodge (1954) and his supplemental pictorial key (figure 156) offer helpful advice and additional information in the use of the CDC key. The California Mosquito Control Association published an illustrated field guide, edited by Ecke (1963), with keys to the adults and larvae of the genera of domestic flies of California. The guide is suitable for persons interested in acquiring an introductory working knowledge of the domestic flies. A 10-power hand lens provides sufficient magnification for observation of all the morphological characteristics utilized in the keys. Information on life cycle and behavior of the most important species is also provided in this very useful publication.

Simple and practical keys such as those just mentioned contain much useful information, and are especially helpful in identifying species in the field. However, any instructor will testify that classroom experience shows that they are far from being infallible aids in keying out species.

Some flies can be recognized by superficial characters. Thus, the bluebottle flies of the genus Calliphora can be recognized by having a metallic blue abdomen but a dull thorax. The flies with dull-gray or brown to black bodies can be separated from those with the entire body shining metallic or black. Within these 2 major groups of flies, wing venation alone separates smaller groups, after which other structural characters are utilized for separating the species of each group.

Flies with the fourth vein angled (figure 156) are either house flies, Musca domestica, which have 4 black stripes on the thorax, or flesh flies, Sarcophaga spp., which have 3 stripes on the thorax. (The cluster fly has the fourth vein angled also, but has no stripes on the thorax.) Flies with the fourth vein gently curved include the stable fly, Stomoxys calcitrans (piercing mouthparts) and the false stable fly, Muscina stabulans (sponging mouthparts). Flies with the fourth vein straight include the little house fly, Fannia canicularis, and the latrine fly, F. scalaris. Flies with the fourth vein sharply angled include the common greenbottle flies (Phaenicia and Lucilia) as well as the black blow fly, Phormia regina. The former have blackish anterior spiracles and relatively large dorsal thoracic bristles, while the latter has reddish anterior spiracles and smaller dorsal thoracic bristles. Within the genera Phaenicia and Lucilia, further separations can be made, and the CDC pictorial key includes the structural characters required (see Phaenicia, at bottom).

House Fly, Musca domestica L. (Muscidae)

The house fly (plate IV, 1) is cosmopolitan within certain latitudes, and is important not only because it annoys man and domestic animals, but also because its habit of crawling on garbage and excrement, as well as on humans and their food, makes it a potential carrier of various disease-provoking pathogens. Pathogens isolated from the house fly include those capable of causing diarrhea, dysentery, typhoid, cholera, poliomyelitis, intestinal worms, eye infections, yaws, anthrax, and tularemia. As with cockroaches, flies have been implicated as vectors of Salmonella bacteria, responsible for food poisoning and gastric infections. The house fly appears to be even more important as a potential vector of Shigella than of Salmonella (James and Harwood, 1969; Greenberg, 1971).

It is not possible to incriminate the house fly as a transmitter of disease organisms with the same certainty with which, for example, Anopheles mosquitoes are identified beyond doubt in the transmission of malaria, or lice in the transmission of typhus. Flies are accused of spreading infections that can also be spread with the fingers or in contaminated food or water. They have been found to harbor over 100 different species of pathogenic organisms, and are charged with transmitting over 65 human and animal diseases, but only on circumstantial evidence. For example, outbreaks of diarrheal diseases are closely correlated with seasonal increases in fly abundance. Also, fly control has been closely correlated with a decline in the incidence of disease. Greenberg (1965) reported, in regard to an experiment made by the United States Public Health Service in Texas, that in towns sprayed with DDT, the rate of dysentery caused by Shigella bacteria declined, whereas in towns left unsprayed as controls, the disease rate remained unchanged. After 18 months, the sprayed towns were left unsprayed and the former control towns were sprayed. The relative incidence of dysentery in the 2 groups of towns was then reversed.

The scarcity of soundly documented cases of field transmission of disease by flies results in inadequate knowledge of how important they are in the natural transmission of the many pathogens commonly associated with them. Therefore, it is still principally the fact that they are annoying to have around domestic premises that motivates us to control them (Anderson, 1966a).

Description. The general size and appearance of the house fly are well known. It is 4 to 7.5 mm long, and may be distinguished from other house-frequenting flies by wing venation, the 4 dark stripes dorsally and lengthwise on the thorax, and the 2 velvety stripes, silver above and gold below, on its face. The eyes of the female are more widely separated than those of the male (figure 157). With its sponging-sucking mouthparts (figure 46, I, in chapter 4), the house fly can ingest only liquid material, but some solid foods can be liquefied by means of regurgitated saliva, and thus ingested. All the aspects of house fly morphology, as well as biology and bionomics, were discussed in great detail by West (1951).

Life Cycle. House flies lay their eggs in warm, moist materials that are suitable for larval growth, such as animal excrement, garbage, piles of lawn clippings, decaying vegetables and fruits, or soil contaminated with such material. Immature stages are shown in plate IV, 1, and figure 158. During warm weather, the eggs, which are laid singly but piled together in small masses, can hatch within a day. The cream-colored larvae (maggots), distinguished by their being narrow at the head end, burrow into the food material in which they hatched, and may complete their 3 instars and pupate in a week or less. As the pupation period approaches, the larvae seek the drier outer regions of their manure pile or other breeding medium, or may leave it to pupate a considerable distance away in the ground, in loose material, or under boards or stones. Under warm conditions, the pupal stage may last 4 to 6 days. Under the warmest natural conditions, a house fly may complete its life cycle in about 8 days, but this period is considerably longer at lower temperatures and when the larvae have had a less than optimum food supply. There may be as many as 10 or 12 generations in one summer. The adult flies generally live from 15 to 25 days, depending on temperature (Roy and Brown, 1954). In colder areas, the adults may overwinter. The potential increase in fly population in a single season is obviously enormous.

Sources of Infestation. In rural areas, piles of manure may be the principal sources of house flies, and in urban areas, piles of fermenting lawn clippings may be important sources of infestation. In garbage cans, blow flies generally breed more abundantly than house flies. The proximity of beef and dairy feedlots and poultry houses to residential areas has become an increasingly frequent cause of complaint and litigation.

People bothered with house flies are interested in knowing whether they live within the flight range of these insects from known sources of infestation, such as those just mentioned. An investigation was made of the flight range of flies that had been fed radioactive materials. Although some house flies were recovered as far as 20 miles from the release site, the bulk of the fly population did not move more than 1 or 2 miles (32,1.6, and 3.2 km) (Schoof, 1959).

Face Fly, Musca autumnalis De Geer (Muscidae)

The face fly is native to Europe and Asia and, since the early 1950's, it has spread to the eastern, midwestern, and southern United States and to parts of Canada. It finally moved westward, until now it occurs throughout most of the country, including the Pacific Coast states, having been found in California near the Oregon border in May, 1968 (Poorbaugh and Smith, 1968). Since then, it has moved steadily southward in California. The face fly received its common name from the habit of the adult of feeding on mucus and watery secretions around the eyes, nostrils, and mouths of cattle, causing great annoyance, reduced production of milk, and additional time necessary to finish beef animals for slaughter.

Description. The face fly (figure 159) is only slightly larger than the house fly, and it is difficult to tell them apart. The males are most easily distinguished, for the eyes of the male face fly almost touch at the top of the head, while those of the male house fly do not. The males are commonly found on certain flowers.

Biology. The face fly breeds only in undisturbed cow droppings, and does not breed in cow manure that has been heaped into piles, mixed with hay, straw, or urine, or that has been tramped on by cattle in crowded feedlots. The opposite is true of the house fly and stable fly - their larvae feed in such disturbed manure but never develop in undisturbed cow droppings in pastures (Anderson, 1966b; Anderson and Poorbaugh, 1968). Mature face fly larvae leave the manure and crawl as far as 30 ft (9 m) before pupating in the soil (Jones, 1969). They are sometimes parasitized by nematodes (Nickle, 1967).

As household pests, face flies resemble the cluster fly (described later in this chapter), for they seek such places as attics, wall voids, or basements as winter harborages, sometimes in enormous numbers. On warm days, many face flies become active and move to the living space of the house.

Stable Fly, Stomoxys calcitrans (L.) (Muscidae)

Another fly that superficially resembles the house fly but rarely occurs in houses is the stable fly. Unlike the house fly, it has a stiff proboscis (figure 46, G, chapter 4) projecting forward from the lower part of the head, enabling both males and females to inflict painful bites and suck out blood. Stable flies normally are serious pests of domestic animals, but on occasion they also attack humans. They are most likely to bite in the region of the ankle. Socks and stockings offer no protection.

Description. The stable fly (figure 160, B) is more robust than the house fly and has a broader abdomen. It can also be differentiated by the difference in wing venation (A and B of the figure), by a prominent, light-colored area between the longitudinal bands in the middle of the thorax, and by the presence of a number of nearly round, dark spots on the upper surface of the abdomen (figure 160, B). When the stable fly is at rest, its wings are held widely apart instead of projecting backward on top of the abdomen, as with the house fly. The stable fly rests with the head cocked upward and abdomen held against the resting surface, whereas the house fly often rests in a crouching position, with head down and body parallel to the surface.

Life Cycle. Stable flies breed in decaying hay, straw, or grain; piles of lawn clippings or rotting fruit; and various manures mixed with grain or bedding. They also breed in the manure of dairy cattle and in poultry droppings when they are "stacked." They are often found in large numbers on beaches, where they lay their eggs in piles of seaweed, and are sometimes called "beach flies." Unlike Fannia species, the immature stages of the stable fly somewhat resemble those of the house fly. In warm weather, adults may emerge in 20 to 25 days after the eggs are laid, but this period can be extended to several months at lower temperatures. (See chapter 9 for a related account.)

False Stable Fly, Muscina stabulans (FallÚn) (Muscidae)

The false stable fly (figure 160, C) superficially resembles the house fly, but it is larger. Note also the difference in wing venation. It is closely related to the house fly, and has similar sponging mouthparts. The female lays her eggs in animal manure, human excreta, and decomposed vegetable matter, including lawn clippings. Twenty-five adult false stable flies were reared from the caked grass taken from beneath the blade guard of a rotary power mower (Ware, 1966). Several generations are produced during the summer months, and hibernation normally takes place in the pupal stage. The females often enter houses to oviposit, scattering from 140 to 200 eggs over various foods, particularly those that are slightly spoiled. Probably it is in this way that man occasionally consumes them and suffers intestinal myiasis (James, 1947).

Muscina assimilis (FallÚn) is darker than M. stabulans, and its legs are entirely black, while those of the latter species are in part reddish brown. In California, M. assimilis is a common species. Adults have been reared from partly decomposed watermelon and other vegetable matter. It is less likely to be found in homes than the closely related Muscina stabulans.

Black Garbage Fly, Ophyra leucostoma (Wiedemann) (Muscidae)

The genus Ophyra contains species that may be found near refuse dumps and poultry ranches and occasionally around cow and hog manures. The adults are not found in or around houses and other buildings, but congregate in trees and shrubs. The larvae are scavengers in decaying vegetation, animal matter, and excrement, but are also known to feed on the maggots of other flies. The black garbage fly (figure 161) is a small, black fly that originally invaded this country from Europe and Asia. One of its larvae may kill from 2 to 20 house fly larvae per day. Fortunately, the Ophyra adults rest at different sites from those frequented by adult house flies. This should make it possible to apply insecticides to sites upon which house flies and other nuisance flies rest, and to avoid those upon which Ophyra adults rest (Anderson and Poorbaugh, 1964).

Little House Fly, Fannia canicularis (L.) (Anthomyidae)

Males of this cosmopolitan fly are often found in houses; the females are rarely found indoors. They are more uniformly distributed than the house flies throughout the average home. In one investigation, 65.6% of house flies, but only 40.9% of little house flies, were found in the kitchen (Peters, 1965). Males of the little house fly tend to fly about aimlessly in the middle of the room or some shaded area outside, often hovering or making jerky, zigzag flights. The little house fly appears earlier in the spring than the house fly, and in regions of high temperature it tends to disappear during the summer. In many areas, this difference is possibly explained by the fact that the little house fly becomes active at a lower temperature (40.1░ F compared with 44░ for the house fly), and also suffers heat paralysis at a lower temperature (105.5 °F compared with 115.7 °for the house fly) (Nieschulz, 1935). (Centigrade: 4.5, 6.7, 40.6, and 46.5 °.) This difference in temperature requirements may account for the fact that in subarctic regions, Fannia canicularis often replaces Musca domestica, and is, for example, the common house fly of Iceland (Chillcott, 1960). This and other species of Fannia are attracted to honeydew, and are often found swarming under aphis-infested vines or trees (Ecke, 1963).

Description. The little house fly (figures 160, D, and 161) resembles the house fly, Musca domestica, but is smaller (3 to 5 mm long) and more slender. The wings in repose are parallel and partly folded over each other, whereas those of the house fly are held in a diverging position. The abdomen of the female F. canicularis is ovoid and gray, while the male's is tapering, with pale yellow, semitransparent patches.

Life Cycle. The little house fly breeds in animal excrement or decaying vegetable material. Floatlike appendages on the eggs (figure 163) enable them to float on top of semiliquid material. The larva has spiny processes along the sides and top of the body. These have fine, whiplike hairs that are said to propel it through semiliquid media (Hickin, 1964). The larvae change from translucent white to light brown as they mature. Like those of the house fly, F. canicularis larvae move to a dryer environment near the surface of their food medium before pupating. The pupae resemble the third-instar larvae, but are darker and somewhat shorter. At 80 °F (27 °C) and 65% relative humidity, the approximate durations of the immature stages were recorded as follows: egg, 1.5 to 2 days; larva, 8 to 10 days; pupa, 9 to 10 days. The period from egg to adult was 18.5 to 22 days, and from egg to egg, 22 to 27 days. About 50% of the male fly population died within 14 days, and 50% of the females died within 24 days (Steve, 1960). In another experiment, the life cycle took 24 to 29 days (Lewallen, 1954).

Latrine Fly, Fannia scalaris (F.)

The latrine fly resembles the little house fly in appearance and life history, but its thorax is bluish black, contrasted to the thorax of Fannia canicularis, which is blackish gray. Also, a grounded protuberance of the median point of the middle pair of legs can be used to distinguish F. scalaris. It prefers human to animal excrement, and has been known to cause myiasis in man.

Coastal Fly, Fannia femoralis (Stein)

This species, of South American origin, is widely distributed throughout the United States. It is a little over half the size of Fannia canicularis, and is shiny black in color (figure 164). It sometimes occurs in large numbers, but is much less important than the little house fly as a pest.

Fannia benjamini Malloch

This species is known from various areas of the West, particularly California. The adult is 3.5 to 4.5 mm long, with a brown-pollinose, unstriped thorax and a dark abdomen without a trace of the yellow translucence found in some species, such as the male of Fannia canicularis. The antennae and palpi are yellow, as are also the legs, with the exception of the black tarsi. The female is much lighter-colored than the male.

The expansion of city suburbs into the foothills, as well as the increasing use of such areas for recreational purposes, is bringing F. benjamini into sharper focus as a pest. It is common in California along streams, particularly in groves of oak trees. It is a very annoying pest, and persists in its attempts to enter the ears, nostrils, and eyes, apparently attracted by perspiration and mucus. This species and F. canicularis have been implicated as vectors of a nematode eye worm, Thelazia californiensis Price. The known hosts of this nematode, besides man, are dogs, cats, horses, sheep, deer, coyotes, and bears (Burnett et al., 1957).

Cluster Fly, Pollenia rudis (F.) (Calliphoridae)

Cluster flies derive their common name from their habit of entering a house in the fall and gathering together in a cluster that may emit a sickly sweetish odor. They tend to gather and hibernate in secluded areas, often in wall voids, and hibernate in them. Cluster flies and face flies (Musca autumnalis) often become trapped in large numbers in wall voids, attracting larder beetles (Dermestes lardarius). The beetles feed on dead flies and then migrate to other parts of the house, causing the occupants to believe they have an infestation of carpet beetles (W. L. Gojmerac, correspondence).

In the spring, cluster flies again become pests as they migrate from wall voids to the living space, via window pulleys, around baseboards, and through other small openings, and then crawl sluggishly over the walls. They are usually found in windows and other out-of-the-way places, and do not fly about noisily like other house-entering calliphorids. In this respect, they are not such nuisances.

Description. Cluster flies (figure 165) closely resemble house flies, but are larger, more robust, and slower in their movements. They are about 8 mm long, dark gray, with checkered black and silvery abdomens, and with many golden hairs on the thoraxes of newly emerged specimens which may be lost in older ones. The stripes on the thorax are not so prominent as those of the house fly. The wings overlap when at rest. Pollenia rudis can be distinguished from all other synanthropic North American calliphorids by its abdomen being nonmetallic in appearance and being covered by a pollenlike dust. A striking characteristic of the biology of cluster flies is that the larvae are parasitic on earthworms. Eggs are deposited in cracks in the soil, hatch in 3 days, and the larvae enter earthworms at almost any point on the body wall. The total developmental period of the fly varies from 27 to 39 days (Webb and Hutchison, 1916). Its breeding habits result in the cluster fly being less of a hazard than other calliphorids as a mechanical carrier of disease organisms (James, 1955).

Control of Cluster Flies

Lawns have been treated with 2.5% heptachlor granules at 3 lb per 1,000 sq ft (1.36 kg per 93 sq m), or with a spray of heptachlor 25% emulsifiable concentrate at 0.25 pt in 3 gal (0.12 L in 11 L) of water per 1,000 sq ft to kill earthworms, and thus prevent the development of cluster flies. The lawn should then be sprinkled to force the toxicant into the soil.

Blow Flies (Calliphoridae)

The blow flies (greenbottle and bluebottle flies) (figure 166) are large scavenger flies, with a metallic blue or green sheen. They may become abundant in and around homes, particularly if they are located near such places as slaughterhouses, meat-processing plants, and garbage dumps. However, it should be borne in mind that some of these insects are stronger fliers than the house fly, and at least a small percentage may travel great distances from the point of dispersal. For example, in one experiment, 13% of the black blow flies, Phormia regina, were trapped between 4 and 28 miles (6.4 and 46 km) from the point of origin, and more than 8% at or beyond 11 miles (18 km) compared with only 3% of house flies trapped at or beyond 4 miles (Schoof, 1959).

Blow flies are most active during warm, sunny weather. When it is cool and cloudy, they tend to retreat to resting sites, usually on vegetation adjacent to areas where they oviposit. Phormia regina tends to disperse more widely than the other species, and in warm weather it often rests on sunlit walls (Busvine, 1966).

Some blow flies, such as Phaenicia sericata and Eucalliphora lilaea (Walker), freely enter houses, and because of their breeding habits and the fact that they feed and oviposit on food, mechanical transmission of disease becomes a distinct sanitary consideration. Meat or fish must be protected from oviposition by blow flies, not only for aesthetic and sanitary reasons, but also because the eggs and larvae of blow flies and some other species, when swallowed, may remain alive for some time, causing acute gastric or enteric disorders (James, 1955).

Blow flies have been known to breed in the carcasses of dead birds or rodents in attics or wall voids of houses. These may be sources, not only of adult flies, but even of the larvae, which are sometimes found crawling about in the living space of the house. Because of their large size, buzzing sound, and tireless flying about throughout the house, blow flies are generally more annoying than house flies. They tend to fly to windows, for like all flies, except perhaps the males of Fannia, they are attracted to bright sunlight.

Although blow flies usually lay their eggs on meat or dead animals, when meat is not present they may oviposit on animal excrement or decaying vegetable matter. One female may lay as many as 600 eggs. Larvae first feed on the surface and then burrow down to less-decayed material. The full-grown larvae burrow into the ground to pupate, usually in the top 5 cm of soil. Tlere are several generations a year. The winter is normally spent in soil by full-grown hibernating larvae.

Some Common Species

James (1955) prepared keys to California species of blow flies, and gave geographical distributions. Some common examples of bluebottle flies are Calliphora vicina (Robineau-Desvoidy) [= erythrocephala (Meigen)] (figure 167, A), C. terraenovae Macquart (plate IV, 2), and C. vomitoria (L.). They are much larger and more robust than the house fly, about 11 mm long, rather bristly, and have metallic-blue abdomens. Eucalliphora lilaea not only enters houses, but sometimes breeds there in the bodies of poisoned or trapped mice, and then occurs in large numbers. A striking variability in the size of this species results sometimes from larval overcrowding (James, 1955). Some bluebottle flies (e.g., C. vicina and C. vomitoria) have been observed to deposit active, newly hatched larvae instead of eggs. Two of the common greenbottle flies, Lucilia illustris (Meigen) [= caesar (L.)] and Phaenicia sericata Meigen (= Lucilia) (fig. 167, B), are about 10 mm long, less bristly than Calliphora, and metallic blue-green. These and many other species occur throughout the United States. Large numbers of maggots of P. sericata dropped onto the bed of a resident of North Hollywood, California, falling from a light fixture in the ceiling over a period of several days. These had bred in the carcass of a dead rat.

The black blow fly, Phormia regina (Meigen) (figure 167, C), is slightly more robust than the greenbottle flies and darker in color. The thorax is almost black, with a metallic bluish-green luster, and the abdomen is darker, being metallic green. Protophormia terraenovae (Robineau-Desvoidy) (figure 167, D) is even darker, and has a purplish cast. The colors of some common blow or bot flies, as well as certain other synanthropic flies, are well displayed in 15 color plates in Flies and Disease, Vol. I (Greenberg, 1971).

Flesh Flies (Sarcophagidae)

The flesh flies are not so likely to enter houses as the related blow flies, but many species, including some carrion and excrement feeders, are considered to be synanthropes (domestic flies). The sarcophagids are medium-sized to relatively large flies. They generally range from about 10 to 14 mm in length, and are robust and dull grayish black, with 3 dark stripes on the thorax. The more familiar species are characterized by a checkerboard pattern of spots that change from black to gray and back with changes in the incidence of light. Sarcophagids are larviparous, i.e., the eggs hatch within the female's body and she deposits the larvae on the food they will be eating. Both the common and family names are derived from the fact that the larvae of most species develop in decayed flesh and spoiling meat, although some kinds can also develop in manure or other animal droppings, and in food residue at the bottoms of garbage cans. The life cycle ranges from 8 to 21 days, and adults may be present from spring through late fall (Loomis et al., 1967).

A representative flesh fly is Sarcophaga haemorrhoidalis (FallÚn) (figure 168). It is nearly cosmopolitan, and in North America it occurs from Oregon to Quebec and south to California and Florida. The adults are 10 to 14 mm long, gray, with the terminalia of the male red. The eyes are reddish brown. The larvae feed on dead insects, carrion, and excrement. Another common and widely distributed flesh fly is Sarcophaga bullata Parker (plate IV, 2). It ranges from British Columbia to Quebec and south to California and Florida (Stone et al., 1965).

Drone Flies (Syrphidae)

The drone flies (Eristalis spp.) are robust, yellowish flies that mimic bees in appearance. They do not cause serious annoyance to man or animals, and rarely enter homes or alight on food. They are often seen around flower beds, the males hovering in the air, almost motionless, but darting swiftly aside when disturbed. Most syrphids are important predators of aphids, but there are also saprophagous genera that are scavengers in semiliquid, rotting vegetable and animal material or, in the case of Eristalis, in putrid or stagnant water or in moist excrement. The larvae are called "rat-tailed maggots" because of the elongate breathing tube that allows them to obtain air even when the remainder of the body is buried in liquid material.

Control of House Flies and Similar Species

The major contribution to fly control is garbage pickup and disposal. In Los Angeles, for example, a city ordinance requires that garbage be wrapped or placed in bags and placed in covered containers to await pickup by the City Sanitation Division once a week, along with prunings, litter, lawn clippings, or other organic materials that are potential sources of fly infestation. The trash and garbage are dumped in areas which are continually being covered with earth by means of giant bulldozers. This is a method of trash and garbage disposal that may be particularly suitable when an earth fill is desired by the community in a particular location, as for filling a ravine or canyon. Incineration is of course a suitable alternative, except where it may contribute substantially to air pollution. City sanitation divisions are relieved of much of the burden of garbage removal by the wide use of automatic garbage-disposal units in the home, for much of the organic waste material thus becomes part of the city sewage.

Not all city ordinances are conducive to maximum fly control. Ordinances pertaining to manure management and disposal or to pest control are helpful only if they are based on sound principles of integrated control, as revealed by the research of qualified entomologists.

Supplementing the community garbage-removal service, decaying organic material and animal excrement on residential property should be deeply buried or otherwise disposed of by the homeowner, for house flies, as well as stable flies, flesh flies, bottle flies, blow flies, little house flies, and false stable flies, all breed in this type of material.

When urban areas are surrounded by areas of high concentration of poultry and livestock, freedom from flies in the city may depend heavily on manure management, water systems [Water dripping from faulty watering systems results in wetter manure and increased fly problems.], general farm sanitation, and the wise use of insecticides in an "integrated control" program in such areas (Anderson, 1965; Burton et al., 1965; Smith, 1969; UCAE, 1971-72).

Exclusion at Doorways

The usual type of window or fly screen (18-mesh) on windows, screen doors, and other openings to buildings is a great help in keeping ingress of flies to a minimum. However, screen doors that must be opened many times during the day cannot be depended upon to completely exclude insects, and may be unsatisfactory where human traffic is heavy or where little, if any, insect entry can be tolerated. In such situations, it is possible to exclude flying insects by means of a downward air current at the doorway. An air speed of 1,500 ft (450 m) per minute, approximately 17 mi (27 km) per hour, when the ratio of the distance through the doorway to its height was 0.37, was found to offer a satisfactory combination of efficiency with economy and acceptability. The installation in the doorway of a removable floor grid or grating that can be readily treated with a long-term residual insecticide or a low-friction finish has been suggested for the exclusion of crawling insects (Hocking, 1960).

Sprays

Two types of spray are generally used for fly control within buildings: space sprays and residual sprays.

Space Sprays. These are applied in order to produce a fine mist that permeates all the air space within a building, so that the insecticide contacts the insects as they are flying about or at rest. The insecticide may or may not break down rapidly; the objective is to contact all the insects in a room and kill them rapidly. A mist can be produced by applying the insecticide in a petroleum base, such as deodorized kerosene (base oil), with an ordinary hand atomizer (figure 9, chapter 3) or any other kind of atomizer. The same objective is accomplished by using an aerosol canister or fogging machine, which generates even smaller droplets, requiring longer for the droplets to settle out of the air. It is desirable to remove pets and ornamental plants and to keep doors and windows closed after treatment for as long as it is convenient. Cover foods and cooking utensils.

Dichlorvos (DDVP) is commonly used for fogging such buildings as food-processing plants, industrial plants, warehouses, and theaters, using 1 gal of a solution containing 10% of toxicant to 64,000 cu ft of space (about 4 L to 1,813 cu m). Manufacturing buildings should not be in operation, and should be vacated and not reoccupied until they have been well ventilated. Food should be removed from the buildings, and food-handling equipment should be covered with draping paper before fogging - or it should be washed after fogging. A suitable mask or respirator should be used by persons applying the fog. Dichlorvos is also applied as a 0.5% spray with a low-pressure sprayer to localized areas that may be infested by flies and other insects that are attracted to food, such as cockroaches and ants. In another procedure, it may be added to a longer-lasting residual spray to obtain rapid knockdown and fuming action in cracks, crevices, and other confined areas, combined with prolonged residual efficacy.

Synergized pyrethrins or allethrin at 0.1% concentration have been used effectively as space sprays, but the newly developed synthetic pyrethroid, resmethrin (SBP-1382«), is as much as 20 times more toxic when used at the same concentration, and no synergist is required. The knockdown rate is slow, but whereas with pyrethrins the flies that are knocked down may recover, with resmethrin they do not. Resmethrin also differs from pyrethrins in that its residues may be effective for several weeks on some types of substrate.

Residual Sprays. These sprays are applied to surfaces upon which flies generally rest. The insecticide is expected to kill flies crawling about on the deposit long after the spray is applied. Great impetus was given to this method of fly control by the original spectacular success of DDT. This insecticide, which came into general use after World War II, was not only highly toxic to house flies and most other household pests, but also had a long residual life. Against house flies, the effectiveness of a spray residue ranged from 8 months on unsized cement surfaces to 18 months on smooth surfaces, such as glass, wallpaper, or finished wood. Within the home, fly control could be obtained for long periods by spraying surfaces on which flies commonly rested, such as window screens. Residual wall and ceiling sprays in barns resulted in about 95% reduction in the fly popiiiation. Flies entering during the day were killed overnight.

Within a few years, house flies developed resistance to DDT and other persistent organochlorine insecticides. Later, the little house fly (Fannia canicularis) was shown to be resistant also. Both species, taken from 3 poultry ranches in southern California, were also shown to be resistant to a number of organophosphorus compounds, but to a smaller degree than to organochlorine compounds. Still, Musca domestica was found to be over 909 times resistant to coumaphos, 182 times to Ciodrin«, 102 times to malathion, and 66.5 times to diazinon. Fannia canicularis was found to be over 174 times resistant to coumaphos, 81.9 times to Ciodrin, 59.1 times to malathion, and 6.8 times to diazinon (Georghiou, 1967). The organophosphorus compounds and carbamates do not have the long residual life inherent in most organochlorine compounds, and resistance is compounding the problem. Diazinon, fenthion, dichlorvos, dimethoate, malathion, naled, and resmethrin are recommended as outdoor space sprays (CDC, 1973). Instructions on labels should be carefully followed when using any of these insecticides.

In California, resistance has not yet developed with Gardona, except on a low level in one area. In Denmark, however, where its use has been more extensive, high resistance is reported. The period required for resistance to appear against a new insecticide is in proportion to the frequency of its.use. This can be delayed by using methods of suppressing the fly population that do not require insecticides, thus reducing the frequency of their application (Georghiou et al., 1972a).

For the control of cluster flies, spraying the outside of a house in the fall with 2% malathion or l% naled or ronnel has been recommended. Particular attention must be paid to the upper third of the wall, the overhang, and the eaves, especially on the south and west sides (Rachesky, 1969). Residual sprays, such as 2% chlordane, have been applied to the surfaces of attics, basements, closets, storerooms, and other areas where cluster flies and face flies are seen, usually with a 2- or 3-gal (7.5- or 11-L) compressed-air sprayer. To avoid staining wallpaper and furnishings, such sprays should not be applied in bedrooms or in papered or well-furnished rooms. Poisonous sprays should also be avoided in food-preparation areas.

A 10% chlordane dust is highly recommended for treatment of places that are difficult to reach with sprays. A 0.5% solution of dichlorvos may be sprayed into window-pulley openings or wall voids (Anonymous, 1970e).

Community Spraying. A community-wide effort in fly control can include spraying. The little house fly, Fannia canicularis, was effectively controlled in one town near a large poultry farm by blowing a mist consisting of 8 gal of DDT 25E and 0.5 gal of malathion 57E per 100 gal of water from roads and driveways over lawns, shrubbery, and onto buildings, at the rate of 1 to 10 gal per acre, depending on vegetative cover (30 L; 2 L; 378 L; 3.8 to 38 L). One application was made in the morning on July 28 and another on September 15 (Hansens, 1963). Although such results can also be obtained with currently registered insecticides if the target species is not resistant, it must be borne in mind that beneficial insect species are also eliminated. In the foregoing example, only a nonvector species was involved, for which most complaints resulted from the activities of the hovering males. In the current climate of ecological awareness, a similar control program would probably not be undertaken. Such community-wide spraying programs should be considered only under emergency disaster conditions. Spraying should not be considered as a substitute for a basic sanitary solution at the sources of infestation.

Insecticide recommendations change as flies become resistant to insecticides. Generally, pyrethrum, with a suitable synergist such as piperonyl butoxide to increase its potency, is added to the currently recommended insecticides, and the combination provides good fly knockdown and kill. With the continually changing statuses of pesticides, an appropriate state official should be consulted for advice as to which compounds are currently registered for the projected treatment.

Other Treatments

A property owner with a fly problem may not be responsible for or have any control over the sources of infestation, but may wish to know what he can do to eliminate the flies on his own property. No great detail on methods and materials will be given here because these are continually changing. A few examples are given, mainly to indicate the types of treatment available rather than specific insecticides. Specific recommendations are revised almost yearly, and are available from university extension personnel or federal and state agricultural extension literature.

The current tendency is to resume the use of space sprays for fly control, or to use baits and "vapor strips." However, according to Rachesky (1970b), Cygon« (dimethoate 25% emulsifiable concentrate) gives 4- to 6-week residual protection during fly season. Treatments should begin in May or June at the rate of 2 gal per 1,000 sq ft (7.5 L per 93 sq m) or to the point of runoff on ceilings, walls, support posts, and outside around closed doors and windows. Rachesky also recommended the use of dimetilan fly bands in garages, under breezeways, in covered porches, and on loading docks. The bands should be wiped occasionally with a damp cloth to remove dust. They are effective for more than a year. No vapors are given off by dimetilan bands; the fly must contact the band.

Dry baits of dichlorvos or dipterex are often very effective in substantially decreasing the fly population, particularly when scattered around garbage cans and outside of doorways. Inside the home, they may be scattered on floors and near windows, according to directions on the labels. The baits should be widely dispersed, to increase the probability that flies will find them and to decrease the hazard to children and pets. Stable flies and most blow flies are not controlled by these baits, but cockroaches, snails, and slugs are susceptible if they happen to be in treated areas (Howell, 1961). Liquid baits, in which molasses, syrup, or sugar are usually the attractants may be applied as sprays, using 1 gal per 1,000 sq ft (about 4 L per 93 sq m), when added to any organophosphorus or carbamate insecticide currently recommended.

Baits tend to have a spectacular but brief effect. A permanent liquid-bait station has been suggested that is merely a chicken-watering unit with a cellulose sponge in the trough to prevent clogging by dead flies. Dichlorvos or trichlorfon at 0.1 % concentration in a sugar/water solution has been used successfully. A constant source of toxicant can be provided by inserting a dichlorvos resin strip in the reservoir jar (CDC, 1972).

In San Bernardino, California, a county sanitarian observed that little house flies (Fannia canicularis) seemed to prefer beer cans to regular garbage. This led to the suggestion that insecticide be placed in about 2 in. (5 cm) of beer in open containers for fly control. This poisoned bait method was found to be effective (Times, 1972). Obviously, the poisoned beer should be placed in locations where it cannot be reached by children.

Dichlorvos resin strips suspended from suitable room fixtures are effective against small, flying insects and are convenient to use. The strip is a solid polyvinyl chloride resin formulation, impregnated with 20% dichlorvos (DDVP) and related products. It is 2.5 in. wide, 0.25 in. thick, and 10 in. long (6 cm; 7 mm; 25 cm). In the period of its activ,ity, the vapor issuing from the strip is highly toxic to insects, but it is rapidly hydrolyzed by moisture. The strips should not be used in kitchens, restaurants, or other places where food is prepared or served, where infants or aged people are confined, or near fish tanks. One strip is sufficient for 1,000 cu ft (28 cu m) of space, and remains effective for weeks. A smaller strip of the same material has been made available. This "ministrip" is only 2 in. (5 cm) long, and is sufficient for a volume of 100 cu ft (2.8 cu m) for the control of such insects as cockroaches, silverfish, .and clothes moths in enclosed spaces. The strips may also be placed in a closed garbage can, attached underneath the lid, for fly control. An additional procedure is indicated when treating for flies, such as cluster flies, face flies, and blow flies, that spend the greater part of the winter in attics, wall voids, and similar enclosed spaces. Insecticide formulations, such as aerosols, silica aerogels, or the currently available combinations of silica aerogel and pyrethrum that can be very thoroughly dispersed, may be used in such areas.

Dichlorvos resin strips may be suspended in attics, closets, and storerooms, provided they have very little air circulation. If the flies work their way into occupied rooms, a space spray or aerosol containing pyrethrum is suggested, repeating as necessary. Sometimes flies in a house will escape if windows are open and the screens removed (Gojmerac, 1969).

Exposure of house flies for 3 days to baited chemosterilants, with light corn syrup as the attractant, resulted in a high degree of sterility with hempa, metepa, and tepa within acceptable limits of adult mortality. With 1 % concentration, 1,00% sterility of males was induced after 72 hours of exposure. The chemosterilants remained active for at least 20 weeks. The tests were sufficiently encouraging to justify further tests in local house fly control with baited chemosterilants alone, and with an integrated program of baited chemosterilants with an insecticide (Pausch, 1971).

Control of Flies on Poultry Ranches

Poultry production is a major nation-wide industry. Flies breeding in poultry manure can be a serious problem when the poultry ranch is situated rather close to urban areas. The most important house pests among these flies are Musca domestica and Fannia canicularis, that develop in manure, and Phaenicia spp., that thrive on fowl carcasses and broken-egg wastes. All can fly considerable distances - up to 20 miles (32 km) and may be attracted to food and shelter in homes and backyards (Peters, 1963).

As already stated, because modern poultry production is a monoculture, natural enemies of poultry pests are at a disadvantage, just as are the natural enemies of plant pests in agricultural monocultures. In plant monoculture, changes in cultural practices and modification of the pest control program in such a way as to avoid the usual need for continually increased dosages of pesticides seem to have been first advocated in 1940 by the Swiss entomologist Schneider (1940), in an extensive monoculture of gambier (Uncaria gambir, family Rubiaceae) in Malaya, and are now generally referred to as "integrated control." This term appears to have been first used by Smith and Allen (1954), who stated: "If we are to escape the ever-tightening spiral of more complex problems and ever-increasing costs of control, then we must integrate chemical control with the natural factors influencing populations." While admitting that many of the strands of the ecosystem of which man is a part remain to be unraveled, they believed: "We are now in a position to take more intelligent steps toward an integrated control program which will utilize all the resources of ecology and give us the most permanent, satisfactory, and economical insect control that is possible." As in the control of plant pests, the current trend in combating pests of poultry and livestock is "integrated control." The number and variety of predators and parasites of filth flies is impressive. The predators include many species of beetles, bugs, flies, ants, earwigs, and mites, and there are some effective hymenopterous parasites (Legner and Brydon, 1966; Legner and Olton, 1968, 1970, 1971). The species that are natural enemies of the flies in accumulated excrement or manure piles are quite different from the ones that are natural enemies of the flies in the undisturbed feces of livestock in pastures. The 2 groups of natural enemies are discussed separately in an extensive review of the subject by Legner and Poorbaugh (1972).

The importance of developing manure removal and pest control practices that result in minimal reduction of the influence of these natural enemies of the pest fly population is obvious. Sound integrated control programs must be preceded by studies on the ecology and behavior of the pest species and the complexity of the ecosystem of which they are a part. An important element of fly behavior studies is the investigation of resting habits during the day and night, indoors and outdoors, in urban and in rural areas, and when buildings are screened or not screened (Kilpatrick and Quarterman, 1952; Maier et al., 1952; Keiding, 1963, 1964). A study in poultry ranches in northern California, in which a backpack vacuum-sampling machine and sticky fly tapes were used, resulted in much information on which species of "domestic" or "filth" flies were involved, which species of natural enemies, and also much useful information on their habits, particularly their resting habits (Anderson, 1964, 1966b; Anderson and Poorbaugh, 1964). In striking contrast to the widespread dispersion of the pest flies during the day, at night all fly species except Phaenicia sericata that remained outdoors rested predominantly on branches of trees and shrubs, and those inside the poultry houses rested predominantly in the general ceiling area. The flies remained at their overnight resting places for 12 to 16 hours, depending on temperature. Sticky tape catches revealed that 85% of resting Fannia canicularis and Musca domestica were caught in houses and 91% of the beneficial predator Ophyra leucostoma and 95% of the ichneumonid parasites were caught in trees and shrubs. The difference in the nocturnal aggregation sites of pest flies and certain of their natural enemies "seems to offer one potential approach to an integrated fly control program on poultry ranches" (Anderson and Poorbaugh, 1964).

The University of California Agricultural Extension Service has published a circular in which integrated control procedures on poultry ranches are recommended (UCAE, 1971-72). A concrete base beneath caged laying hens to catch droppings prevents house flies from pupating in the soil. Natural enemies can then destroy a greater percentage of immature flies. During the season when flies are a problem, only the top portion of manure should be removed, and a 6- to 8-in. (15- to 20-cm) pad should remain on the concrete base, or all manure may be removed on an alternate row basis. In either case, natural enemies from the manure that remains can quickly invade adjacent fresh droppings. If all manure is removed at one time, a period of 6 to 12 months is required to reestablish the natural enemies.

If insecticides are required, they should be applied only to overhead and peripheral portions of the poultry houses. If droppings are sprayed, nearly all the natural enemies that normally infest droppings will be killed. These natural enemies can destroy more than 95%of the fly population. Residual insecticides directed against adult flies and applied to the ceilings and peripheral parts of the poultry houses do not interfere with key natural enemies (Legner and Olton, 1968). Great care should be taken to avoid contamination of feed and water. Diazinon, dieldrin, lindane, and trichlorfon are no longer labeled for use in poultry houses (CDC, 1973).

In an attempt to control flies on poultry ranches without long-range residue buildup and adverse ecological effects, the relatively new organophosphorus insecticide Rabon's (table 1, chapter 2), in an encapsulated formulation mixed with the feed, has been fed to poultry, and this passes through the bird without being assimilated to any appreciable extent. It causes complete mortality of fly larvae in the manure, while leaving no residues in body tissues of the poultry or in the eggs (yolks) (Wasti and Shaw, 1971). Another organophosphorus insecticide, coumaphos, mixed with cow feed, showed promise in the control of house fly larvae in the manure, and the experiments have been continued (Miller et al., 1970).

In one investigation, a dichlorvos formulation (20% Shell Vapona Resin Strip Regrind) successfully controlled fly larvae and adults for about 7 weeks with 3 applications of 2 g of actual toxicant per square meter of breeding area in Florida poultry houses containing caged layers. The investigators emphasized that concurrent treatment of 2 life stages of the flies might speed up the development of resistance to the insecticide, and they believed that an alternative chemical that would be equally effective against both stages was needed (Bailey et al., 1971). However, advocates of integrated control do not believe that insecticides should be used in this way on poultry ranches, not only because of the possibility of rapid development of resistance, but because the treatment is nonselective and kills all beneficial species. They suggest that its use should possibly be restricted to the wet "hot spots" where the greatest concentrations of larvae are found (J. R. Anderson, correspondence).

On the other hand, some investigators have felt that certain insecticides could be used advantageously on poultry droppings. Rodriguez et al. (1970) found that diazinon, ronnel, Bayer 38156, and malathion, when applied to poultry manure, were effective against fly larvae and relatively nontoxic to predatory mites [Glyptholaspis confusa (Foa), Macrocheles muscaedomesticae (Scopali), and Fuscuropoda vegetans (De Geer)]. Control of the house fly in poultry manure by these mites, under semifield conditions, ranged from 86 to 99%, depending on the species of mite. The use of sugar-based baits against adult flies was another approach to the integrated control program (Rodriguez et al., 1970). Also, cockerels were allowed to run freely under caged hens, and the only food they obtained was what they could find, primarily fly larvae (Rodriguez and Riehl, 1959a, 1962).

Vinegar Flies (Drosophilidae)

These very small flies are cosmopolitan, and are usually known as vinegar flies. They are so small that they can pass through ordinary "flyscreen," and are therefore common pests in homes, restaurants, fruit markets, canneries, cellars, or basements containing fermenting liquids (vinegar, cider, wine, beer), and in other places that contain attractive food materials.

Description. All the economically important species are superficially similar in appearance (figure 169). They are dull brownish yellow or brownish black in their over-all aspect. A feathery bristle on the antenna helps to distinguish Drosophila from other small flies. The adult of the best-known species, D. melanogaster Meigen, is 3 mm long, with red eyes, tan-colored head and thorax, and the abdomen is blackish on top and grayish underneath. Other species that commonly become pests are D. funebris (F.), D. repleta Wollaston, D. buschii Coquillett, D. affinis Sturtevant, D. falleni Wheeler, D. tribunctata Loew, and D. hydei Sturtevant.

Life Cycle. Vinegar flies lay their eggs near the surface of fermenting or rotting fruit and vegetable material or in unclean garbage cans. The pearly-white, cylindrical eggs, which can be observed with a hand lens, have 2 to 4 threadlike filaments at one end, and these filaments protrude above the liquid material in which the eggs are laid. The tiny maggots crawl out of the liquid food to some drier substance, preferably loose soil, to pupate. The brown, seedlike pupae have 2 hornlike stalks at the anterior end. About 500 eggs are deposited by a single female, on an average, and since the life cycle may require only 8 to 10 days in warm weather, the reproductive potential is enormous.

Control of Vinegar Flies

The most important aspect of Drosophila control is the elimination of food and breeding sources. This refers not only to the most obvious materials, such as piles of rotting and fermenting fruits and vegetables, but also to such sources as peelings accidentally swept under appliances or counters, discarded ketchup or milk bottles that have retained a portion of their contents, dishwater or water from floor mappings that has seeped into crevices, garbage-laden water from sinks, or a foul, soured mop. Vinegar flies constitute a serious problem in rural communities that are close to extensive sources of the insects, such as tomato fields or canning plants. Cannery sanitation is extremely important. Egg deposition in boxes of tomatoes in the field or on pallets in the receiving stations of canneries can be prevented for a 24-hour period by the application of pyrethrum dust, principally because of its repellent effect (Stombler et al., 1957).

Piles of culled fruit are important sources of vinegar flies and driedfruit beetles (Carpophilus spp.). These pests can be controlled by suitable insecticides, such as liquid sprays or granular formulations. Insecticide granules have to be mixed into the mass of fruits if the pile is more than 24 in. (60 cm) deep. Larvae can be prevented from developing long enough for the fruit wastes to become too dry to attract insects. Sprays of azinphosmethyl, fenthion, or trichlorfon, or granular formulations of malathion, endrin, or heptachlor have proved to be effective (Yerington, 1969). For control of vinegar flies in wine cellars, a thermal aerosol of 0.25'% pyrethrins, combined with either piperonyl butoxide or Tropital« as synergists, was found to be effective, but treatments once or twice daily were required to keep the insects under control (Yerington, 1971).

Substantial reduction in vinegar fly populations in tomato fields was obtained by releasing large numbers of the adult flies of both sexes that had been sterilized with 1% aqueous apholate, a well-known insect chemosterilant. The investigators stated that release of sexually sterilized flies in a program such as they described "shows promise of controlling D. melanogaster in commercially grown tomatoes, especially if the program is conducted on a community-wide basis" (Mason et al., 1968).

In the home, space sprays, aerosols, or dichlorvos resin strips, as they would be used for house fly control, have been effective against vinegar flies.


ANTS


Ant Species List


Ants are among the most common pests of the home. Their nests are found almost everywhere - in lawns, under the house, in the walls of the house, in open ground, under stones or wood, in wood of decaying trees, or in other locations that afford protection. Ants are social insects of the order Hymenoptera, and live in colonies. They cannot live alone, but unlike other social insects (termites, wasps, and bees), they are not dependent on a definite habitation, but can quickly transport their eggs, larvae, and pupae to a more favorable location when necessary. With the exception of the males, ants share with termites the advantage of a long life span and comparative freedom from natural enemies.

Ants enter buildings when seeking sweet or fatty substances in the kitchen, pantry, storeroom, or warehouse. They may also be pests of the lawn or garden because of their nesting habits or because they may destroy plants, seeds, fruits, and nuts. Ants may feed on the sugary excretion (honeydew) of certain plantsucking insects, such as aphids, psyllids, mealybugs, unarmored scales, cottonycushion scales, whiteflies, and treehoppers. In crawling. back and forth over the infested plant, the ants interfere with activities, such as oviposition, of the natural enemies of these pests. In addition, ants actually destroy adult parasites and the larvae of predators. They may also carry aphids and other honeydew-excreting insects to plants in order to establish colonies of them. Control of ants is a great aid in garden pest control.

How to Recognize Ants

The principal body regions of ants are distinctly defined by narrow constrictions (fig. 170). The elbowed antennae are composed of a scape (long basal segment) and a funicle or funiculus (terminal segmented portion). At the end of the antenna, the last 1 to 4 segments may be enlarged to form the "antennal club." The abdomen is attached to the thorax via 1 or 2 slender segments that are parts of the abdomen, and form the petiole or pedicel. Each segment of the petiole has a bump or node on its dorsal surface, as can be seen in the drawings in this section. Some genera have 2 nodes (e.g., Pogonomyrmex, Veromessor, Pheidole, Crematogaster, Monomorium, Solenopsis, and Tetramorium), and other genera, higher in the evolutionary scale, have 1 node (Liometopum, Iridomyrmex, Dorymyrmex, Tapinoma, Camponotus, Paratrechina, Prenolepis, Lasius, and Formica), so the number of nodes is one of the morphological features by which an ant can be identified. The remainder, and major portion, of the abdomen is called the gaster. It may consist of 7 or 8 segments, the male having 1 more than the female.

Keys to the genera and species of the ants of North America were prepared by Creighton (1950).

The Ant Castes

Ants have 3 distinct castes (queen, male, worker), and there may be different forms in each caste. The soldier is a large worker. The head and mandibles of the soldier and the thorax of the queen are very large in comparison with those of other forms and castes. Ants are generally wingless, but at mating time swarms of winged males and females (figure 176) usually emerge from the nests, although the reproductives of some species, such as the Argentine and Pharaoh ant, mate and remain in the nest. Those emerging from the nests mate while in flight, and the male dies a day or two later. The females (queens) lose their wings and attempt to establish new colonies after digging a nest in the ground or seeking a cavity under some object, such as a stone or piece of bark. The workers or neuters are sterile females, and. may vary greatly in size. They are very different from the females in appearance. They do all the work of the colony, such as building the nest, caring for the queen and the young, and providing food.

Trophallaxis is common among the higher ants. The workers gather food, chew and prepare it, then feed it to the larvae. The larvae digest the food and regurgitate the digested food for the adults to consume. Such ants are often seen moving their larvae about from place to place; they are then "carrying their stomachs around." Adult ants, in common with adult bees and wasps, can feed on liquid foods such as nectar and honeydew. They have powerful mandibles that can pierce and chew fruits, seeds, and other insects. However, adult ants have a very slender esophagus and a very small proventricular opening that do not admit the chewed-up particles. The larvae must digest such food and feed the adults (Went et al., 1972).

Ant Trails

In the intensive investigation of insect pheromones in the last 2 decades, odor-trail pheromones have received their share of attention. Among the ants, these chemicals originate in several different glandular tissues. In 3 subfamilies, odor-trail pheromones originate in the hindgut. In the dolichoderine ants, these pheromones originate in Pavan's organ, where they are probably synthesized. In some myrmicine ants, trail pheromones arise in glands-associated with the stinger, e.g., Dufour's gland of the imported fire ant, Solenopsis invicta. In some other myrmicine genera, the venom-gland secretion itself is utilized to lay odor trails. In the myrmicine genus Crematogaster (acrobat ants), the trail pheromone is apparently produced in a tibial gland which presumably evacuates through the pretarsus. Some ants emit both volatile and nonvolatile trail pheromones, and are able to lay a trail that will be long-lasting but will also recruit workers quickly (Blum, 1970). Some species, such as the Florida harvester ant, Pogonomyrmex badius, utilize odor trails as well as sun orientation, whereas landmarks are of minor importance. Some other species, such as Cataglyphus bicolor, orient mainly to visual landmarks, utilizing sun orientation only when the landmarks become ineffective (H÷lldobler, 1971). The foraging column of Veromessor needs sunlight to orient itself. Many of the foragers break out of the column and wander about aimlessly if they encounter a patch of shade more than a half-meter long (Creighton, 1953).

H÷lldobler and Wilson (1970) observed that a scouting ant of the genus Pogonomyrmex held its abdomen upward in ordinary locomotion, but returned from a successful scouting trip with its abdomen completely lowered and dragging the extruded stinger over the surface of the ground so as to leave a scented trail for others to follow. They proved that P. badius used recruitment pheromones released from the venom gland and orientation or homing pheromones released at least in part from Dufour's gland.

The source of the trail pheromones of the ponerine ants Leptogenys attenuata Smith and L. nitida Smith is the venom sac of the stinging apparatus. When given a choice, the ants of these 2 species preferred to follow the trail pheromone of their own species, but were also able to follow the trails of the other species (Fletcher, 1971).

M. S. Blum (Smith, 1965) stated that the workers of Iridomyrmex pruinosus deposit on their foraging trails a methyl-n-amyl ketone substance, and that workers can be induced to follow artificial trails containing the scent of this compound. The Argentine ant, Iridomyrmex humilis, relies heavily, if not completely, on scent when following trails. Olfactory stimuli are received in sites located in the funicle, possibly primarily in the first 2 segments (Dechene, 1970).

Ant Bites and Stings

Some species, such as the harvester ants (Pogonomyrmex) and fire ants (Solenopsis), inflict severe stings. Others merely bite, but they may curve their abdomens forward to inject a secretion into the wound and are, therefore, thought to be stinging (e.g., Formica and other Formicinae). The Formicinae are the only ants that secrete formic acid, emptying it into the wound. The venom of ants that sting does not contain formic acid, neither does the venom of wasps and bees; therefore, local application of alkalies results in no relief from pain when one is stung by such insects (Keele, 1963).

Ants that have stingers normally use their venom offensively only to kill prey, but if the nest is attacked, they may use the venom defensively to repel the intruders. The species known principally for their bites or stings are discussed in chapter 9, and the carpenter ants are discussed in chapter 5. In the present chapter, only the species are discussed that are pests mostly because they nest in the house or invade it from the outside, and became nuisances by getting into household foods.

Argentine Ant, Iridomyrmex humilis (Mayr)

Argentine ants were first found in the United States in New Orleans in 1891, and now range throughout the southern states as well as California, where they first appeared in 1905. In California, they may be found at the lower elevations in moist locations in urban areas and orchards. There is no record of their presence in Arizona (J. N. Roney, correspondence). These ants invade the home in columns, seeking sweets, and may be traced back to their nests, that are usually in the ground, although they can also nest in treeholes, refuse piles, bird nests, or beehives, to name a few possibilities. Argentine ants bite, but do not sting. This species is not only the most common pest in the home, but is also an important agricultural pest because of its interference with the activities of natural enemies of aphids and similar plant pests as it crawls over a plant in search of honeydew.

Description. The worker is light to dark brown (plate II, 5), 2.2 to 2.6 mm long, and its petiole has 1 node (figures 170, A, and 171). The queen is brownish, with a silky pubescence, up to 6 mm long, and is usually wingless. The male is shiny brownish black, winged, less robust than the female, and is up to 5 mm long. There is no perceptible odor if an individual ant is crushed, but if large numbers are crushed, the Argentine ant has a "greasy" or musty odor. In this respect it differs from another common house-infesting ant, the odorous house ant, Tapinoma sessile, which also seeks sweets and travels in trails. One can detect the pungent odor of this species by crushing only a single individual (Eckert and Mallis, 1941).

Life Cycle. There are few winged females and consequently few mating flights. Mating generally takes place in the nest, after which the male is eliminated from the nest. There are many reproductive females in the colony, and each lays a large number of eggs. That is the reason for the enormous numbers of individuals produced. The period required for the completion of the life cycle varies greatly with temperature, moisture, nutrition, and other factors, but has been obsserved to vary from 33 to 141 days, with an average of 74 days (Eckert and Mallis, 1941).

During the winter, Argentine ants tend to congregate at greater depths in the soil, down to about 6 in. (15 cm), or in such locations as manholes or basements kept warm by steam pipes. They begin to increase in numbers toward the end of February, and reach their maximum number during July, August, and September. During this period, they have gradually spread out over larger areas, particularly in well-moistened locations such as under shrubbery and along the edges of walks. The nests are then usually from 0.5 to 1.5 in. (12 mm to 4 cm) below the surface. By the middle of October, they have again noticeably decreased in number (Eckert and Mallis, 1941). Argentine ant nests are sometimes under buildings, and soil treatment for subterranean termites is also valuable in ant control.

Markin (1970a, b) made a 3-year study of the seasonal life history of the Argentine ant in 6 California citrus orchards, but primarily in a 5-acre (2-ha) block of Valencia orange trees with a slightly southern exposure. The orchard had received no insecticide treatments in more than 10 years. There was an ant nest for each tree in the orchard, but the nests were not permanent structures. Adverse conditions such as flooding or drying resulted in the ants moving to other nesting sites or joining adjacent colonies. Nests were connected with trails, and workers could sometimes be seen carrying the brood or queen from one nest to another.

A great many eggs are produced in late February to early March, and mostly sexual forms develop from them. The sexual forms mature in May, and mate within the nest soon after the females emerge from the pupae. The females then shed their wings and oviposit. The number of queens in the nest remains fairly constant until January or February of the following year, when about 75% of them are killed by workers. Workers are first produced about mid-March, and increase in numbers until a seasonal high is reached in October, when production of workers decreases sharply. The number of workers then decreases steadily, reaching its lowest level the following March or April (Markin, 1968, 1970a, b).

Habits. The Argentine ant tends to drive out other ant species wherever it becomes established. When in conflict with species of greater fighting ability, several Argentine ants will attack a single victim, and in that way will make up by their superior numbers what they may lack in fighting prowess.

In the "flash floods" of southern California, these ants have been seen to mass into balls and float down the stream, thus disseminating the species along the course of the streambed.

The workers forage at all times of the day and night, in either light or darkness. They become sluggish at 7 °C (about 45 °F), and cease activity entirely at 6 °C (43 °F), but immediately become fully active when again exposed to warmer temperatures (Dechene, 1970). Argentine ants will leave their nests to forage at temperatures from 10 to 30 °C (50 to 86 °F). They prefer sweet foods, and are remarkably adept at finding them and rapidly establishing their trails. They will also feed on both live and dead insects, meat, injured fruits, seeds, and cereals, particularly cornmeal. These ants have been observed killing adults and nymphs of conenose bugs (Triatoma) in small jars, cutting them into bits small enough to pass through the 1.5- to 3-mm holes of the perforated jar lids, and carrying the insect bits to their nests (S. F. Wood, personal communication). They have also been observed killing all active stages of German cockroaches (Blattella germanica) in rearing jars and carrying away the comminuted fragments (D. A. Reierson, personal communication).

In addition to invading the home, Argentine ants are common garden pests, for they are among the species that are attracted to honeydew, a sugary liquid excreted by aphids and related plant pests. One investigation in a southern California citrus orchard revealed that honeydew and nectar comprised more than 99% of the material carried into the nests by the workers (Markin, 1970a). Argentine ants are among the species, already referred to, that can interfere with the activities of hymenopterous parasites, kill the larvae of predators, and thereby increase insect infestation of plants. The ants can also carry aphids and other sapsucking, honeydew-producing insects to plants in order to infest them. Control of Argentine ants may substantially diminish or even eliminate pests that excrete honeydew as well as others that may be benefited by the decrease in their natural enemies when ants are present.

Iridomyrmex pruinosus (Roger)

This is a native species that ranges from Wisconsin to New York, south to New Mexico and Florida, and also occurs in Colorado, Arizona, Utah, Nevada, California, Oregon, and Idaho. It is common and widely distributed in the southern United States. It infests houses, particularly in the Gulf Coast states, generally invading them from outside, but is also believed to be able to nest within a house (Smith, 1965).

Description. As shown in figure 170, B, this species can be distinguished from the Argentine ant by the difference in the shape of its head, the presence of erect hairs on the thorax, and by having a more densely pubescent body. The body color (plate II, 5) is variable. In the eastern states, this species is commonly uniform dark brown or black, whereas the body of the Argentine ant is usually light to dark brown (Smith, 1965). In the western states, the body color is even more variable, some specimens being even lighter in color than Iridomyrmex humilis (R. R. Snelling, personal communication). The workers are 1.8 to 2.5 mm long. The odor of crushed specimens of I. pruinosus is like "rotten coconut," similar to the odor of the odorous house ant (Tapinoma sessile), whereas a mass of crushed specimens of I. humilis has a stale and musty or greasy odor.

Habits. Iridomyrmex pruinosus prefers open spaces, such as fields, meadows, pastures, or entirely bare areas, but will also nest in open woods away from dense and prolonged shade. The nests may be constructed in exposed soil or under cover of stones or the bark of logs and stumps, and contain small to moderate-sized colonies. Like the Argentine ant, this species feeds on live or dead insects, is particularly fond of honeydew, and forms foraging trails.

Harvester Ants (Veromessor spp.)

These ants are predominantly black, and have conspicuous thoracic spines. The petiole has 2 nodes. Their habits are somewhat similar to those of Pogonomyrmex (chapter 9), except that they do not sting, their stinger being vestigial and nonfunctional. Homeowners object to their nests in yards and lawns. They are very active, and harvest large quantities of seeds.

Longspined Harvester Ant, Veromessor andrei (Mayr)

This species (figure 170, C, and 172) is 4.5 to 7 mm long, with a reddish-brown head and thorax, and in some specimens the posterior part of the abdomen is black. The remainder of the body is lighter in color - in southern California, generally reddish brown. It is limited almost entirely to California in its distribution. Wheeler and Wheeler (1973) point out that while V. andrei does not sting, its bite is quite tenacious and annoying.

Jetblack Harvester Ant, Veromessor pergandei (Mayr)

This species (figure 170, D) is 2.5 to 6 mm long, and as the common name indicates, is a beautiful "jet-black, patent-leather-colored" ant (Mallis, 1941a). It inhabits the deserts of southern California, northwestern Arizona, and Baja California. The nests of V. pergandei are usually surrounded by a crater of excavated soil, whereas those of V. andrei usually are not. Veromessor pergandei makes a neat pile of chaff with seed husks in the form of a semicircle or ring around the nest, whereas V. andrei makes a more ragged pile or scatters the chaff about. Veromessor pergandei can tolerate the most extreme heat of the deserts, but V. andrei cannot.

Bigheaded Ants (Pheidole spp.)

These ants are so named because of the exceptionally large heads of the soldiers in relation to their bodies. They live in situations somewhat similar to those inhabited by fire ants, have similar habits, and are distributed throughout the warmer areas of the United States. As in the case of the fire ant, the petiole has 2 nodes. They resemble fire ants superficially, but can be distinguished from them by their 12-segmented antenna, 3-segmented antennal club, and the large head, particularly of the soldier. The natural foods of Pheidole spp. are generally live and dead insects, seeds, and honeydew, but in houses they will feed on meats, grease, peanut butter, fruit juice, and other foods.

Western Bigheaded Ant, Pheidole hyatti Emery

This species (figure 170, E) may be found throughout the San Joaquin and Sacramento valleys of California, as well as in most of the state below 3,000 ft (900 m) elevation, and east to Texas. These ants are 3 to 6 mm long, uniformly light to dark reddish, with the soldiers sometimes darker and more brownish than the workers. The soldier's head is deeply furrowed in the frontal view. The body has abundant long hairs. Pheidole hyatti is common in arid and semiarid areas, and makes nests in the soil, often beneath stones and boards. It is usually nocturnal, and is omnivorous, with a decided tendency to be predaceous (R. R. Snelling, correspondence). The ants are sometimes found in and around houses; in kitchens, they are usually found around the sink. They are especially fond of greasy meats.

Acrobat Ants (Crematogaster spp.)

Acrobat ants are characterized by the heartshaped abdomen, the upper surface of which is flattened and the lower surface curved. They may be black, brown, or yellow, and the petiole has 2 nodes. Their common name is derived from their habit of raising the abdomen over the head and thorax (figure 173, bottom). They are slow moving ants that tend aphids, and are known to construct "tents" or "cowsheds" of earth and vegetable debris over the aphids from which they obtain the sugary excrement known as "honeydew" (Wheeler, 1906; Eckert and Mallis, 1941; Matheson, 1951). They are generally found under stones or in old stumps, and have sometimes been found to tunnel and nest in wood (Mallis, 1969). They occasionally become pests by invading houses.

Lined Acrobat Ant, Crematogaster lineolata (Say)

This ant ranges from southern Canada southward along the Rocky Mountains and eastward to Florida, and has been found at altitudes up to 5,500 ft (1,700 m). It varies in color from light brown through dark brown to black. The scape (first segment) of the antenna extends beyond the posterior border of the head. The workers are 2.5 to 3.5 mm long. Medium-sized to large colonies may nest in exposed soil, under stones or other objects, or in logs, stumps, and dead trees. The ants may also nest in the woodwork of houses and infest household foods, where they show a slight preference for sweets and meats or other high protein foods. In nature, they feed on honeydew and dead or live insects, including winged termites. The workers bite aggressively, and give off a repulsive odor when alarmed (Smith, 1965).

California Acrobat Ant, Crematogaster californica Emery

This species occurs in southern California and Baja California, nesting in soil or rotten wood at elevations below 3,500 ft (1,060 m) (figures 170, F, and 173). The workers are 2.5 to 3.5 mm long. The head and thorax may be reddish and the gaster black, but the head and thorax may be variably infuscated. One or two erect hairs occur on the pronotal shoulder. These ants are both diurnal and nocturnal. They tend aphids and mealybugs on both foliage and roots. They are attracted to sweets (R. R. Snelling, correspondence).

Pharaoh Ant, Monomorium pharaonis (L.)

This species is native to Africa, but has been spread by commerce to nearly every part of the world. The specific name, from which the common name was derived, resulted from Linnaeus' mistaken belief that the ant was one of the plagues of Egypt in the time of the Pharaohs, mentioned in Scripture, whereas the only plagues mentioned were lice, flies, and locusts (Riley, 1889).

Although the Pharaoh ant occurs throughout the United States and Canada, it is rarely found in California, but appears to be established in at least 2 locations in the state (M. S. Wasbauer, correspondence). It has never been identified as a household pest in California, but is important in some other parts of the country. It is especially common in hotels, large apartment houses, grocery stores, or other places where food is commercially handled. In residential areas, nests may be found outdoors in the lawn or garden and indoors in wall voids, subfloor areas, attics, cracks, crevices, and behind wainscoting, baseboards, plaster, or mantles, under hearthstones, between flooring, or in furniture. The ants tend to seek warm and inaccessible locations. They breed throughout the year, and produce enormous numbers of individuals. They feed on dead and live insects, and often damage the dried specimens in collections. In the home, they appear to prefer grease, fats, and meats, but are practically omnivorous. In the early years of American agriculture, they caused great damage to crops. For example, they injured young corn plants by gnawing the blades and drinking the sap (Forbes, 1920).

Monomorium pharaonis has become particularly well adapted to existence in close association with man by abandoning the nuptial flight and territorial boundaries. Colonies multiply by "budding." If groups of these ants in a large building are joined by odor trails, they may constitute a widely dispersed colony that can contain up to millions of workers and thousands of queens (Bellevoye, 1889; Wilson et al., 1971).

Description. The Pharaoh ant (figure 174, A) is one of the smallest ants, 1.5 to 2 mm long, and is light yellow to reddish in color. The petiole has 2 nodes. It is often confused with the thief ant, Solenopsis molesta, but averages slightly larger, and can be distinguished by 3 segments in the antennal club, compared with 2 in the thief ant.

Life Cycle. Although the usual sexual forms are winged, nuptial flights have never been seen. Mating takes place in the nest, and the formation of a new colony is not normally accomplished by a single female after a nuptial flight, as with many other ant species. Instead, a large part of a colony will migrate to a new location, the workers carrying with them eggs and young stages. In this way, new nests can be developed throughout a building, and such nests have been found to contain from 400 to 4,800 ants (Smith, 1965; Busvine, 1966).

Peacock and Baxter (1949) developed procedures and equipment for rearing colonies of Monomorium pharaonis in the laboratory. In subsequent investigations (Peacock and Baxter, 1950), they found that the various life stages of the workers required the following numbers of days: egg, 5 to 6; larvae, 22 to 24; prepupal, 2 to 3; and pupal, 9 to 12; thus, the life cycle required 38 to 45 days at room temperature. Sexual forms required about 4 days longer. The maximum period of adult life of the workers was 9 to 10 weeks, females lived as long as 39 weeks, and males generally not more than 3 weeks. The females were able to lay from 350 to 450 eggs.

Habits. Pharaoh ants crawl great distances from their nests, and do not always follow definite paths. Therefore, the nests may be difficult to find, increasing the difficulty of control. A shipowner spent $4,000 in trying to eradicate Pharaoh ants from his vessel. They have been stated to be the most persistent and difficult of all our house-infesting ants to control (Smith, 1965).

An interesting aspect of Pharaoh ant infestation is their tendency to nest in odd places, as between sheets of stationery, layers of linen, between clothing in trunks, in an electric iron, in a can of modeling clay, or, in piles of trash.

Many investigators have noted the tendency of the Pharaoh ant to be attracted to water, such as from dripping faucets, and one observer noted that their trails to the earth beneath the house did not necessarily indicate the presence of a nest, for the ants might be seeking moisture in the soil (Mallis, 1969).

Little Black Ant, Monomorium minimum (Buckley)

This small, jet-black species (figure 174, B) is 1.5 mm long. Its petiole has 2 nodes. It is found throughout the United States. In California, it occurs in the southern part of the state and in the San Francisco Bay area. These ants may nest beneath rocks, in rotting wood, in lawns, or in open areas, where the nests are indicated by very small craters of fine soil. Their colonies are usually moderate to large, and contain many fertile females. Males and winged females may be seen from June to August. The workers are predaceous on other insects, tend honeydew-producing insects, and feed on honeydew as well as nectar and pollen. There have been reports of recently hatched bluebirds and kingfishers being killed by these ants. They may either invade a house from the outside, or establish their nests in the woodwork or masonry of the building. In the house, they feed on both sweets and greasy foods (Smith, 1965).

Thief Ant, Solenopsis molesta (Say)

Thief ants are found over most of the United States, and have been found at altitudes up to 5,500 ft (1,700 m). In nature, the nests of S. molesta and other tiny thief ants are usually located so that extremely narrow passages from the thief ant nests communicate with the nest passages of a larger ant species. The common name of the thief ant was derived from its habit of steadily pilfering the brood and other food from the nests of larger species (Creighton, 1950). The stinger of the thief ant is rarely used. Although they are in the genus Solenopsis, thief ants are not considered to be "fire ants." The latter are discussed in chapter 9.

Description. The workers (figure 174, C) are very small, 1.3 to 1.8 mm long, among the smallest ants in the United States. Tle workers are monomorphic (1 form only). The petiole has 2 nodes. The body is largely smooth and shiny, and ranges from yellowish to light or dark brown. Thief ants superficially resemble Pharaoh ants, but are smaller, lighter in color, and the antenna has a 2-segmented rather than a 3-segmented club. The antennal club is unusually large and elongate, about 1.33 times the length of the remainder of the funiculus. The scape of the antenna extends farther than between the eye and the posterior border of the head (Smith, 1965).

Biology. The outdoor nesting habits of the thief ant are similar to those of other Solenopsis species. There may be several hundred to a few thousand ants in a colony. In nature, they nest in exposed soil or under stones and other objects, and in rotting wood. Copulation takes place during nuptial flights, which have been observed from late July to early fall. A single fertile female is able to establish a nest (Eckert and Mallis, 1941; Smith, 1965).

Habits. Workers are predaceous, and feed on both live and dead insects. They also feed on planted or germinating grains, often causing considerable damage. They seek honeydew and tend honeydew excreting insects. Because they feed on dead rats and mice, they may be carriers of disease-producing organisms to food. They are known to attack young chicks in poultry houses (Eckert and Mallis, 1941). Workers have been seen carrying gravid segments of the poultry tapeworm, Raillietina tetragona (Molin), into their nest, suggesting that the ants may be intermediate hosts for the tapeworm (Smith, 1965).

When they are found in the home, thief ants usually have their nests in wall voids or elsewhere in the house rather than entering from outside. Their extremely small size enables them to enter containers not accessible to larger ants. They often infest pantries, cupboards, cabinets, and shelves, even though these have been kept closed and scrupulously clean. They are often found around sinks. However, they are so small that they are sometimes not seen, even when crawling on food.

Thief ants will eat practically anything, but appear to prefer foods with a high protein content. They have more of a tendency than the Pharaoh ant to feed on greases, but will eat sweets also (Eckert and Mallis, 1941; Smith, 1965).

Pavement Ant, Tetramorium caespitum (L.)

This species occurs in most of the eastern half of the United States and in California, where it occurs in both the San Joaquin and Sacramento valleys. Nests occur under stones, along edges of curbing, and in cracks in the pavement. The nests may or may not be surrounded by craters. When nesting in houses, these ants are most likely to be found around or between the lower masonry walls of the foundation. In some areas of the eastern states, the pavement ant is considered to be the most important ant pest in houses, where it may be found throughout the year, but in greater numbers during the summer (Mallis, 1969). It feeds on both greasy and sweet foods.

Description. This species is 3 to 4 mm long, and its body varies from light to very dark brown, with lighter legs and antennae. The head and thorax are furrowed with parallel lines (figure 174, D), and the posterior dorsal portion of the thorax bears a pair of small spines. The petiole has 2 nodes. The entire body is covered with stiff hairs.

Velvety Tree Ant, Liometopum occidentale Emery

The principal pest in the genus Liometopum is the California velvety tree ant, L. occidentale. This species has been observed in northern California east to Colorado and south to central Mexico (R. R. Snelling, personal communication). In foothill and mountain areas, the trails of this species may extend 200 ft (60 m) or more from the base of a tree or log to a house, where the ants search for sweets and insects. Sometimes velvety tree ants enter a house where a tree limb is in contact with it; the limb should be removed. Although the ants may be seen prowling about during daylight hours, they make their forays for food at dusk or during the night (Eckert and Mallis, 1941).

There is only 1 other species in the genus, L. apiculatum Mayr, which ranges throughout approximately the same areas as L. occidentale, except that it does not occur in California.

Description. This species (figure 174, E) is 2.5 to 6 mm long, with a glistening, velvety-black abdomen, red thorax, and brownish-black head. Except for the 2 species of Iridomyrmex, which because of their economic importance and well-known biologies were used to introduce the ant section of this chapter, the preceding ant species all have petioles with 2 nodes. Species of Iridomyrmex and Liometopum, and all remaining species to be discussed in this chapter, have petioles with 1 node.

Habits. Throughout California, this ant occurs in large colonies in the crotches or hollows of trees, in stumps, and in the ground beneath stones. The insects can be found crawling up trails, up and down oak, alder, elm, sycamore, cottonwood, and other trees, particularly along streams, foraging for insects and honeydew. Areas along streams and under trees also happen to be popular picnic grounds, and the velvety tree ant is therefore the bane of picnickers - biting people, crawling over their food, and producing a disagreeable odor when crushed. The removal of decayed portions of ornamental or shade trees in which the ants nest helps to eliminate these pests.

Pyramid Ant, Dorymyrmex pyramicus (Roger)

This small ant is occasionally encountered at lower altitudes throughout California, where it nests in dry and vegetation-free areas. The earth excavated from its nest and gallery system is in a circular crater, usually about 2 to 4 in. (5 to 10 cm) or larger in diameter. It invades the home from the outside, feeds on a wide variety of household foods, but seems to prefer sweets (Eckert and Mallis, 1941). This species is widely distributed over most of the United States, but is more common in the southern half.

Description and Habits. The pyramid ant (figure 174, P) is 1.5 to 2.0 mm long, and has a reddish-black head and thorax and black abdomen. Its common name was suggested by the pyramidlike projection on the thorax. The petiole has 1 node. The workers travel in trails, and are fastmoving. They seek honeydew on garden plants, but are also carnivorous and predaceous.

Bicolored Pyramid Ant, Dorymyrmex bicolor Wheeler

This species (figure 175, A) is similar to D. pyramicus, of which it was once considered to be a variety, but it is slightly larger and has a red head and thorax. It is found in the same geographical areas as the pyramid ant and in similar locations, but is of very little importance as a pest (Eckert and Mallis, 1941).

Odorous House Ant, Tapinoma sessile (Say)

The odorous house ant, so named because of its unpleasant odor when crushed, occurs throughout the United States, from sea level to 10,000 ft (about 3,000 m) elevation. It is second only to the Argentine ant as a household pest. However, in areas where the Argentine ant is also found, the odorous house ant tends to become less common or to disappear entirely. Nevertheless, it still frequently invades homes or apartments in southern California. Tilden (1969) pointed out that the odorous house ant had a tendency to invade houses late in the year when the honeydew upon which it generally fed became less abundant. Also, rainfall and leaf fall, which reduce the numbers of aphids and other honeydew-excreting insects, may induce the ants to enter houses in search of food. It is most likely to invade houses during rainy weather. This ant does not possess a stinger.

Description. The odorous house ant workers (figure 175, B) are 2.4 to 3.25 mm long-slightly larger than the Argentine ant. The petiole is a single segment, with the node vestigial, flattened or inclined, and concealed from above by the base of the gaster. Like the Argentine ant, the odorous house ant travels in trails, and it also seeks the same kinds of food, preferring sweets. It can be distinguished from the Argentine ant by its darker color (uniform brown to black), broader abdomen, by the fact that the petiole and its 1 vestigial node are hidden by the abdomen, and by its odor when crushed. Its pungent, "rotten-coconutlike" odor is detectable even when only a single individual is crushed.

Biology. The odorous house ant nests in many types of habitats - sandy beaches, pastures, woodlands, and bogs. It can also locate in buildings, and often nests in wall voids, particularly around hot-water pipes and heaters (Tilden, 1969). Its nests may be under stones or logs, but also under loose bark, in plant cavities, insect galls, refuse piles, and bird or mammal nests. In the soil, the nests are shallow and indefinite in form (Smith, 1965). The number of ants in a colony may range from a few hundred to many thousands, and there may be many reproductive females. Mating usually takes place in the nest, but nuptial flights have been observed. Lone females (figure 176) have been observed to establish a colony, although Smith (1965) believed that colonies might also be formed when 1 or more fertile females left the parental colony accompanied by a number of workers. An average colony was found to have 345 eggs, 829 larvae, 533 pupae, 2,319 workers, and 1 to 6 dealated females (Wang and Brook, 1970).

Habits. As just mentioned, the workers travel in trails. They are very active, and have rapid movements. When alarmed, they dash about in an erratic manner, and the entire gaster is elevated. Odorous house ants are avid seekers of honeydew, and have been observed to transport honeydew-excreting insects such as aphids and mealybugs. They also feed on both live and dead insects. Although they will eat almost any type of household food, they prefer sweets.

Crazy Ant, Paratrechina longicornis (Latreille)

This introduced species, possibly of Oriental or African origin, is now almost cosmopolitan, and is frequently intercepted in plant quarantine. It is common in the Gulf Coast region, especially in Florida, but is also well established in many towns and cities throughout the United States, including California. In the colder regions of the country, it occurs mainly in apartment buildings, hotels, and greenhouses, and can be a pest all year. Its common name axises from the worker's habit of running in a haphazard manner, as if lacking a sense of direction (Smith, 1965).

Description. The workers are 2.2 to 3.0 mm long. They have slender bodies, with very long antennae and legs (figure 175, C). The antennae are 12-segmented, and do not have a club. The body is dark brown to black, with a "peculiar gray to violaceous luster or sheen," and has long, coarse hairs. The petiole has 1 node. The insect has no stinger. (Smith, 1965.).

Habits. Outdoors, the crazy ant nests in trash, cavities in trees, rotten wood, and in the soil under various objects in colonies of moderate to large size, but it can also nest in buildings. The workers run very rapidly, and can even jump, according to some observers. Their keen sense of smell enables them to find food quickly. They are almost omnivorous, feeding on live and dead insects, seeds, honeydew, fruits, plant exudates, and many household foods. In Puerto Rico, workers of P. longicornis have been reported to be predaceous on the larvae and adults of the house fly, flesh flies, and other Diptera (Pimentel, 1955). They have been observed to attack the larvae of the oriental rat flea (Xenopsylla cheopis) under laboratory conditions, indicating that they may be important in reducing flea infestations under natural conditions (Fox and Garcia-Moll, 1961). On the debit side, the workers are also known to gather small seeds of such crops as lettuce and tobacco from seedbeds, and their fondness for sweets forced the proprietor of a soda fountain in Florida to discontinue business (Smith, 1965).

False Honey Ants (Prenolepis spp.)

False honey ants occur throughout the United States. The workers are 3 to 4 mm long, light to dark brown, very shiny in appearance, and have a somewhat triangular abdomen. They seldom invade the home. Their name probably comes from their habit of feeding on honey, honeydew, and nectar until their gasters are greatly extended, almost as much as those of the honeypot ants (Melophorus) of Australia and of Myrmecocystus of the United States Southwest. (The "repletes" of these species store honey in their gasters, and are sources of sweets for primitive people.) However, honey ants also feed on the exudates of oak galls, live and dead insects, the fluids of dead earthworms, and the young, tender tissues of plants.

Small Honey Ant, Prenolepis imparis (Say)

This species ranges throughout much of the United States, is common in California, and often replaces the Argentine ant where the latter has been exterminated. When these ants are found in houses, they have usually come from outdoors, but it is likely that they often nest inside, for on many occasions winged females and males have been collected inside houses from January to March (Smith, 1965). This ant lacks a stinger and seldom bites, for it is not aggressive. A striking characteristic of Prenolepis imparis is that it is most active outdoors at temperatures between 35 and 55 °F (2 and 13 °C), and has been observed to emerge from its subterranean galleries at 6 °F (-14.4 °C) (Wheeler, 1930).

According to Smith (1965), worker ants feed on such household foods as "sweet corn, corned beef, meats, cakes, breads, sugar, honey, syrup, watermelon, and fruits, but are especially fond of sweets." Outdoors, the ants can damage flower buds. H. M. Armitage observed Prenolepis imparis feeding extensively on tender, young growth and the calyxes and unopened petals of orange buds in southern California (Wheeler, 1930).

Description. Prenolepis imparis varies in color from pale to dark brown or black, with the head and thorax often lighter in color than the abdomen. The body is smooth and shiny. The thorax is small, slender, and almost cylindrical, and is divided into 2 parts by a strong constriction (figure 175, D). The abdominal petiole is composed of a single segment (1 node). The antennae are 12-segmented, do not have a club, and the scape extends beyond the posterior border of the head by half the length of the scape.

The Nest. This ant normally constructs its nest in soil, preferably moist clay or loamy soil in shady woodlands, but seldom under stones or other objects. The nest has a central opening, surrounded by a crater of characteristic earthen pellets. A single gallery leads to the nest, which may be from 18 to 51 in. (45 to 130 cm) deep and have 6 to 40 lateral chambers leading from it. There are seldom more than a few thousand ants in a colony (Smith, 1965).

Life Cycle. In winter, an old colony contains a single reproductive female, winged males and females, and many workers. Usually in March to April, the overwintering males and females make their nuptial flight, although most of the mating appears to take place on the ground. The female then discards her wings and seeks a crevice in the ground in which to oviposit and start a new colony (Smith, 1965).

Species of Lasius

The Lasius species are relatively unimportant in California. The workers are monomorphic, active, emit a strong formic acid odor, but do not have a stinger. The antennae are 12-segmented and lack a club. The eyes are well developed, and are located closer to the posterior border of the head than to the base of the mandible. If ocelli (simple eyes) are present, they are small and indistinct. The abdominal petiole has only 1 segment, and the petiolar node is narrow in profile and either vertical or not strongly inclined (figure 175, E and F).

Lasius niger (L.) and
L. pallitarsis Provancher (= sitkaensis)

In California, these 2 species are usually found in evergreen forests. They have similar habits, nesting in soil or rotten logs. They forage either diurnally or nocturnally. They are strongly attracted to sweets, and tend mealybugs and aphids, especially on roots. Lasius niger (figure 175, E) is 2.6 to 4.1 mm long, and uniformly medium to blackish brown, the scapes of the antennae tending to be yellowish brown. The body is moderately hairy. This species occurs throughout most of the West. In California, it ranges from the northeastern area southward along the Sierra Nevada to the San Gabriel Mountains. Lasius pallitarsis (figure 175, F) is 2.5 to 4.5 mm long, and is similar to L. niger, but is hairier and its color is more variable, ranging from yellowish brown to dark brown. Whereas in L. niger the basal tooth of the mandible is on the same plane as the rest of the teeth, in L. pallitarsis the basal tooth of one or both mandibles is offset, i.e., not in line with the other teeth. Lasius pallitarsis ranges throughout the mountainous areas of the western United States, and also transcontinentally across the northern states and southern Canada (R. R. Snelling, correspondence).

Control of Ants

Recognition of species is important in ant control. The odorous house ant and thief ant may nest in houses, and their trails will lead to the nesting areas, which can then be treated. When they nest in large, inaccessible areas, such as attics, wall voids, and voids under cabinets, dusting with a chlordane or silica aerogel dust may be the most convenient and also the most effective way to obtain complete coverage and good control. Although the Argentine ant nests outdoors, it infests houses more frequently than any other ant species. The housewife may wish to treat for Argentine ants indoors in order to get rid of them quickly, but for effective and long-term control of this and other outdoor-nesting species that may invade the house, the main reliance should be placed on outdoor treatment.

The Argentine, odorous house, thief, jetblack harvester, field, and velvety tree ants travel in trails, and the trails help to trace them to their nests. Repeated spraying or dusting of trails can result in good ant control. Some ants are attracted to sweets only (Argentine, field, and velvety tree ants), and the thief ant is usually attracted to fats only. For a discussion of field ants, see chapter 9, under "Ants (Formicidae)".

The other species discussed in this section are attracted to both sweets and fats, except for the harvester ants (Veromessor) which eat mainly seeds. A knowledge of the food habits of ants is necessary in order to decide on what type of bait to use when control is to be accomplished by the use of poison baits.

For control of ants within a house, sprays of 2 to 3% chlordane applied with a sprayer or paintbrush to baseboards and cracks where ants are seen, or a 50% chlordane dust applied behind baseboards or in out-of-sight areas, are effective. It may be most convenient to apply an aerosol containing chlordane, holding the canister close to the sprayed surface so as to wet it visibly. If ant trails are found outside the house, a spray or dust may be applied next to the foundation in the general area of infestation. Aphid-tending species of ants, like the Argentine ant, may be controlled in yards and gardens by spraying or dusting the ground under the infested shrubs or trees. The shrubs or trees themselves should not be sprayed, for they may be injured and natural enemies of the pests may be destroyed. This should not only help to control the honeydew-producing insect pests that are favored by the presence of ants, but should also decrease the ant population in the general area of the home and thereby decrease the chance of infestation in the house.

A "hose-attachment" sprayer (figure 11, chapter 3) is a great convenience, and is a time-saver if large areas need to be sprayed. Best results can be obtained with power sprayers, such as those used by commercial pest control operators, to spray the entire area around a house where nests may be located as well as tree trunks and subfloor areas. Some operators control ants by periodically spraying the entire foundation and the adjacent soil.

The homeowner can effectively use baits, such as 0.125% Kepone« or 0.075% mirex, placing them in ant-nest openings, around foundations, and in other areas frequented by ants. It is important to use the proper percentage of toxic ingredient when placing ant baits. For example, dieldrin at 0.05% concentration in syrup gave complete control of the odorous house ant, but at 0.5 and 1%, the baits were repellent and the ants would not feed on them. Dieldrin happens to have amazing toxicity against the odorous house ant - it required a 67 times greater concentration of chlordane to obtain an equal mortality level (Wang and Brook, 1970). However, dieldrin is no longer registered for such household uses.

Poisoned syrups are still commercially available for ant control, and are effective against species attracted to sweets, such as the Argentine ant. The receptacles containing the syrup should be placed at intervals of 10 to 20 ft (3 to 6 m) around the foundation of the house. The syrups contain sodium arsenite, and it is not advisable to use them if children or pets are in the vicinity.

For the control of Pharaoh ants in hospitals, where they are considered to be potential carriers of disease germs, Eichler and Kleinsorge (1973) found baiting with arsenicals to be the only fully effective procedure. One successful bait had the following ingredients: ground beef, 1,000 g; arsenic, 200 g; and honey, 80 g; mixed by hand, using rubber gloves. Ground liver was the most attractive bait, and did not require the addition of honey. However, it dried out too rapidly in warm rooms, and was therefore more effective when mixed with beef. The bait was placed in locked wooden bait stations. Ground meat was left 3 days before poison bait was used, to accustom the ants to the new food station. Baits were renewed as often as required to avoid a dry bait surface. If an ant trail was disturbed during the baiting period, the insects fled to their nest, and it took several days for them to re-establish a trail to the bait station.


Figure Captions

Fig. 148. Female German cockroach, Blattella germanica, with attached o÷theca shortly before it was dropped.

Fig. 149. Developmental periods for 4 species of cockroaches at a constant temperature of 82 °F (28 °C) and relative humidity of 70% (shorter bar in each pair) and at ordinary room conditions. Reduction in size of bar for the oriental cockroach indicates a possible 2-year cycle for some individuals. (From Gould and Deay, 1940.).

Fig. 150. Characteristic resting position of a German cockroach in a narrow crevice. (From P. B. Cornwell [1968], The Cockroach, courtesy Hutchinson Publishing Group, Ltd.).

Fig. 151. O÷thecae of the brownbanded cockroach, Supella longipalpa, as they are characteristically deposited in clusters on vertical surfaces.

Fig. 152. American cockroach, Periplaneta americana (nymph).

Fig. 153. Median longitudinal section of a German cockroach that had been left on a deposit of stained boric add until "knockdown." The dark intestinal contents show the point reached by the boric acid within the intestinal tract.

Fig. 154. Truck-mounted, gasoline-powered centrifugal blower for applying insecticide dust into the sewer system. Fig. 155. Pictorial key to common domestic flies in the United States. (From Scott and Littig, 1962.) Fig. 156. Morphological characters of the generalized fly (top) and numbered wing veins (bottom) used for identification of species. (From Dodge, 1954.).

Fig. 157. Head and thorax of the male (left) and female house fly, showing difference in width of space between eyes. (Photo by Stennett S. Heaton, courtesy Shell Chemical Company.).

Fig. 158. House fly, Musca domestica. Eggs, larva, newly developed pupa, and older pupa. (Each division of the scale below represents one-sixteenth in., or about 1.5 min.).

Fig. 159. Face fly, Musca autumnalis. (Drawing by Ruth DeNicola.) Fig. 160. Domestic flies (females). A, house fly, Musca domestica, B, stable fly, Stomoxys calcitrans; C. false stable fly, Muscina stabulans; D, little house fly, Fannia canicularis. (From B. Greenberg [1971], Flies and Disease, courtesy Princeton University Press.).

Fig. 161. Black garbage fly, Ophyra leucostoma (female). (From B. Greenberg [1971], Flies and Disease, courtesy Princeton University Press.).

Fig. 162. Little house fly, Fannia canicularis. Left to right: adult female; pupa; dorsal (left) and ventral views of larva. (Photo by Stennett S. Reaton, courtesy Shell Chemical Company.).

Fig. 163. Eggs of little house fly, Fannia canicularis (left) and coastal fly, Fannia femoralis. (Photo by Stennett S. Heaton, courtesy Shell Chemical Company.).

Fig. 164. Coastal fly, Fannia femoralis. Top left, adult female; top right, pupa; bottom, dorsal, lateral, and ventral views of larva. (Photo by Stennett S. Heaton, courtesy Shell Chemical Company.).

Fig. 165. Cluster fly, Pollenia rudis. (Drawing by Ruth DeNicola.).

Fig. 166. A blow fly (Calliphoridae).

Fig. 167. Blow flies (females). A, Calliphora vicina; B, Phaenicia sericata; C, Phormia regina; D, Protophormia terraenovae. (From B. Greenberg [1971], Flies and Disease, courtesy Princeton University Press.).

Fig. 168. A flesh fly, Sarcophaga haemorrhoidalis (female). (From B. Greenberg [1971], Flies and Disease, courtesy Princeton University Press.).

Fig. 169. Vinegar fly, Drosophila melanogaster (female). (From B. Greenberg [1971], Flies and Disease, courtesy Princeton University Press.).

Fig. 170. House-infesting ants. A, Argentine ant, Iridomyrmex humilis, B, Iridemyrmex pruinosus; C, longspined harvester ant, Veromessor andrei, D, jetblack harvester ant, Veromessor pergandei; E, western bigheaded ant, Pheidole hyatti, F, California acrobat ant, Crematogaster californica. (Courtesy R. R. Snelling.).

Fig. 171. Argentine ant, Iridomyrmex humilis (worker).

Fig. 172. Longspined harvester ant, Veromessor andrei.

Fig. 173. California acrobat ant, Crematogaster californica.

Fig. 174. House-infesting ants. A, Pharaoh ant, Monomorium pharaonis; D, little black ant, Monomorium minimum, C, thief ant, Solenopsis molesta; D, pavement ant, Tetramorium caespitum E, velvety tree ant, Liometopum occidentale; F, pyramid ant, Dorymyrmex pyramicus. (Courtesy R. R. Snelling.).

Fig. 175. A, bicolored pyramid ant, Dorymyrmex bicolor; D, odorous house ant, Tapinoma sessile; C, crazy ant, Paratrechina longicornis, D, small honey ant, Prenolepis imparis; E, Lasius niger; F, Lasius pallitarsis. (Courtesy R. R. Snelling.).

Fig. 176. Winged females of the odorous house ant, Tapinoma sessile.


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