Adults are about 1/2-5/8 inches in length. They are light brown to tan except for 2 dark longitudinal stripes on the pronotal shield. Females are darker than the males, her abdomen is also broader than his. They rarely do fly.
Nymphal instars 1-2 with thorax dark brown to black but having pale lateral margins. Meso- and metathorax pale or white centrally but with a continous dark stripe near each margin. The thorax and abdomen is a light brown ventrally. Later instars have 2 dark longitudinal stripes on pronotum continous with dark abdomen, and abdominal segments usually with central areas pale on dorsum.
The egg capsule is yellowish brown but usually two-toned. Its paler end is attached to the female and about 1/4-3/8 inches long. The length of the capsule is more than twice the width. Subdivisional furrows extend the entire width and the capsule is slightly bowed. Each capsule hold about 15-20 eggs on each side.
German cockroaches are found throughout structures but show a preference for warm and humid areas. They are usually found in kitchens and secondarily in bathrooms. Infestations often occur in rooms where people eat and drink (i.e. the den, bedroom, kitchen, etc.). Any crack located near a source of food and/or water is prime feeding grounds, and they spend about 75% of their time in such a place. First instar nymphs require a crack of about 1/32 of an inch, whereas adults require a crack of about 3/16 inches in width.
These cockroaches are most commonly introduced into building via paper products (i.e. grocery bags, cardboard boxes, drinking cartons, etc.). They can also be introduce via secondary appliances such as refrigerators, televisions, microwaves, etc. They have been observed to migrate from building to building on warm evenings, but this rarely occurs. They can survive outdoors during the warm months but this is uncommon. They feed on almost anything with nutritive value including all kinds of food, and such things as soap, glue and toothpaste.
Activity periods vary with life stage, age, and physiological state. The reproducing females are quite active whereas the gravid (with egg capsule) females are relatively inactive starting about the 5th day after mating and go only to food and water when necessary. Males spend most of their time near the feeding grounds, even at night. All nymphs become immobile and stay near the feeding grounds during the last 3 days of each instar while they molt. About 1/3 of the time the cockroach nymphs will not be found during the inspection.
The female carries her egg capsule until it is within 1-2 days of hatching. She then deposits it in a sheltered area. On the average, the female will produce between 4-8 capsules, each holding an average of 30-40 eggs.
Developmental time usually varies from 54-215 days, average time is 103 days. In the course of a year there will be 3 to 4 generations, with up to 6 adults. The adults will live about 100-200 days. Seventy-five percent of the German cockroach population is composed of nymphs.
Blattella germanica Linnaeus