American Cockroaches

Scientific name: Periplaneta americana (Linnaeus) (Insecta: Blattodea: Blattidae)

Distribution:

Forty-seven species are included in the genus Periplaneta, none of which are endemic to the U.S. (Bell and Adiyodi 1981). The American cockroach, P. americana, was introduced to the United States from Africa as early as 1625 (Bell and Adiyodi 1981). The American cockroach has spread throughout the world by commerce. The cockroach is often found residing indoors as well as outdoors. It is found mainly in basements, sewers, steam tunnels, and drainage systems (Rust et. al. 1991). This cockroach is readily found in commercial and large buildings such as restaurants, grocery stores, bakeries, and where food is prepared and stored. The American cockroach is rarely found in houses, however after heavy rain infestations of the cockroach can occur in homes. They can develop to enormous numbers, greater than 5,000 sometimes being found in individual sewer manholes (Rust et. al. 1991).

Description

Egg: Females of the American cockroach lay their eggs in a hardened, purseshaped egg case called an ootheca. About one week after mating the female produce an ootheca and at the peak of her reproductive period, she may form about two ootheca per week (Bell and Adiyodi 1981). The females on average produce an egg case about once a month for ten months laying 16 eggs per egg case. The female deposits the ootheca near a source of food by either simply dropping it or gluing it to a surface with a secretion from her mouth. The deposited ootheca contains water sufficient for the eggs to develop without receiving additional water from the substrate (Bell and Adiyodi 1981). The egg case is brown when deposited and turns black in a day or two. A typical egg case contains about 14 to 16 eggs. It is about 8 mm long and 5 mm high.

Larva or Nymph: The nymphal stage begins when the egg hatches and ends with the emergence of the adult. The number of times an American cockroach molts varies from six to 14 (Bell and Adiyodi 1981). The first instar American cockroach is white immediately after hatching then becomes a grayish brown. After molting instars of the cockroach nymphs are white and then become a uniformly reddish-brown with the posterior margins of the thoracic and abdominal segments being a darker color. Wings are not present in the nymphal stages and wig pads become noticeable in the third or fourth instar. Complete development from egg to adult is about 600 days. The nymphs as well as the adults actively forage for food and water.

Adult: The adult American cockroach is reddish brown in appearance with a pale-brown or yellow band around the edge of the pronotum. The males are longer than the females because their wings extend 4 to 8 mm beyond the tip of the abdomen. Males and females have a pair of slender, jointed cerci at the tip of the abdomen. The male cockroaches have cerci with 18 to 19 segments while the female has 13 to 14 segments. The male American cockroaches have a pair of styli between the cerci while the females do not.

Life Cycle

The American cockroach has three life stages: the egg, a variable number of nymphal instars, and adult. The life cycle from egg to adult averages about 600 days while the adult life span may be another 400 days. The immatures emerge from the egg case in about six to eight weeks and mature in about six to twelve months. Adults can live up to one year and an adult female will produce an average of 150 young in her lifetime. Environmental factors such as temperature and humidity can increase or decrease the developmental time of the American cockroach. Outdoors the female shows a preference for moist, concealed ovipositon sites (Bell and Adiyodi 1981).

Diet

The American cockroach is an omnivorous and opportunistic feeder. It consumes decaying organic matter but since the cockroach is a scavenger it will eat most anything. It prefers sweets and has been observed eating paper, boots, hair, bread, fruit, book bindings, fish, peanuts, old rice, putrid sake, the soft part on the inside of animal hides, cloth and dead insects (Bell and Adiyodi 1981).

Medical and Economic Significance

American cockroaches can become a public health problem due to their association with human waste and disease, and their ability to move from sewers into homes and commercial establishments. In the United States during the summer, alleyways and yards maybe overrun by these cockroaches. The cockroach is found in caves, mines, privies, latrines, cesspools, sewers, sewerage treatment plants, and dumps (Bell and Adiyodi 1981). Their presence in these habitats is of epidemiological significance. At least 22 species of pathogenic human bacteria, virus, fungi, and protozoans, as well as five species of helminthic worms, have been isolated from field collected American cockroaches (Rust et. al. 1991). Cockroaches are also aesthetically displeasing because they can soil items with their excrement and regurgitation.

Management:

Several hymenopteran natural enemies of the American cockroach have been found (Suiter et. al. 1998). These parasitic wasps deposit their eggs in the cockroach ootheca preventing the emergence of cockroach nymphs. parasitic wasps

Other means of management are insecticides that can be applied to basement walls, wood scraps, and other infested locations. Residual sprays can be applied inside and around the perimeter of an infested structure. When insecticides and sprays are used to manage cockroach populations they may ultimately kill off the parasitic wasps. Loose, toxic, pellet baits are extremely effective in controlling America cockroach populations.

Egg Capsules

American cockroach egg cases are about 38 mm long. They are dark-colored—reddish or blackish brown. Homeowners often find these egg cases in basements, in laundry rooms or kitchens. The egg cases may be under cabinets or behind appliances. American cockroaches also deposit their egg capsules behind stored items in garages and sheds.

Odor

Cockroaches produce a chemical called an “aggregation pheromone.” The odor of this chemical causes the roaches to stay together in groups. Some people describe the odor of these pheromones as having a “musty” smell. As the roach population starts to grow, people with sensitive noses may begin to notice this odor.