"The Oriental Cockroach" (Blatta orientalis)

Hebard (1917), in discussing this insect, notes: "In infested houses around Philadelphia it appears in swarms during the month of May, coincident with the arrival of the shad in the Delaware River, and in consequence is locally known as the Shad cockroach." Very often this cockroach, as well as other species, is called a "water bug," possibly because cockroaches inhabit damp places, but it should be remembered that a water bug is merely a "cockroach" in the poorer parts of the city, but a "water bug" in Beverly Hills. In some parts of the world the oriental cockroach is referred to as the "black beetle."

This species, which is less wary and more sluggish than the others, is the most disliked of all cockroaches since it often travels through sewer pipes and lives on filth. It may enter the home in food packages and laundry, or merely come in under the door or through air-ducts or ventilators. Nixon (1984) found that large populations of this cockroach are common in trash chutes, and Thoms and Robinson (1986) discovered large populations in wall and porch voids. The oriental cockroach is most common in dark, damp basements, but is known to climb water pipes to the upper floors of apartment houses. Since high-rise apartments no longer allow the burning of garbage, oriental cockroaches have a free highway to climb to upper floors via garbage chutes. Thoms and Robinson (1986) demostrated that oriental cockroaches tend to remain near their preferred harborage site, and that barrier treatments of encapsulated insecticide in June (in Virginia) provided control through the summer activity period.

At times large numbers of oriental cockroaches occur in one great mass around leaks in the basement or crawl space areas of homes. By increasing ventilation it is possible to decrease the dampness beneath homes and thereby greatly reduce infestations. This is notable, gregarious species which, according to Howard and Marlatt (1902), lives "together in colonies in the most amicable way, the small ones being allowed by the larger ones to sit on them, run over them and nestle beneath them without any resentment being shown."

The oriental cockroach is so dark brown in color that, as was previously noted, it is often referred to as the "black beetle" in both the United States and England. The adult is 1 inch in length. The male has fully-developed wings, but apparently does not fly. The female has rudimentary wings which are reduced to mere lobes. The mature female may be distinguished from the large nymph by the fact the wing stubs have a definite venation. Laing (1938) states the abdomen of the female is broader than the male and appears to be dragged along the floor when the insect is in motion, while the male keeps its body clear of the ground when running. The male can be recognized by the styli between its pairs of jointed cerci; the females are far more numerous and pairing takes place at any season.

The female may carry the brown egg capsule for 30 hours. A full compliment of 16 eggs can be laid in the egg capsule, which consists of two rows of eight eggs each. Gould and Deay (1940), who studied the life history of this species, found the average number of nymphs to hatch per egg capsule to be 14.4. The female may deposit from one to 18 egg capsules with an average of eight per female. The egg capsule is carried from 12 hours to five days and then deposited in some warm sheltered spot where food is readily available. In this species the female cockroach gives no assistance to her newly born young. At room temperature, the incubation period was 42 to 81 days, with an average of 60 days. Rau (1945) showed this cockroach prefers to feed upon starchy foods.

In England, Zabinski (1929) observed the developmental period to be 12 months, during which interval the insect undergoes seven molts. He found there is a seasonal history for this species since the adults appear in May, June and July. Gould and Deay (1940), who studied this cockroach in Indiana, noted the smaller cockroaches became more and more evident during the summer months. In Souther California the oriental cockroach was observed on sidewalks during the summer months. The time it took the oriental cockroach to complete development in the laboratory varied from 311 to 800 days. Capsules were produced from December to August. No adults matured during the months of October, November and December. The adult females may live from 34 to 181 days.