German cockroaches are 1/2 to 5/8-inches long when mature, light brown to tan, and have fully developed wings. The pronotum (i.e., shield like segment behind the head) has two dark parallel bars on it. The adult males are somewhat narrower that the females when viewed from below. The nymphs, 1/8-inch long when they emerge from the egg capsule, are almost uniformly dark except for a light tan area on the back of the second and third segments. As they develop, the light tan area becomes longer until, as mature nymphs, they have two parallel black bars separated by a light tan area. The purse shaped egg capsule of the German cockroach (i.e., ootheca) is light brown in color, ¼ to 3/8-inch long, and typically has 15 to 20 eggs per side.
During her lifetime, the female German cockroach produces four to eight egg capsules each of which contains 30 to 40 eggs. The female carries the egg capsule partially within her abdomen until just before the nymphs are ready to emerge. Approximately one to two days before hatching, she drops the egg capsule in a protected area. If the egg capsule is dropped prematurely, the developing roaches inside dies of dehydration. Nymphs molt six to seven times before becoming adults. This requires about 103 days; thus allowing three to four generations per year. Adults live 100 to 200 days. Established German cockroach populations consist of approximately 75% nymphs.
German cockroaches are the most common household insect within the United States. This pest typically infests kitchens and bathrooms but will live anywhere inside heated structures in which there is food, water, and harborage. They rarely are found outdoors and then only during warm weather. German cockroaches gain entry into structures in grocery bags, cardboard boxes, drink cartons, infested equipment such as used refrigerators, toasters, microwaves, etc. Cockroaches feed on all types of human food, as well as on pet food, toothpaste, soap, glue, etc.
German cockroaches are active at night, leaving their harborage to find food and water. They remain hidden in dark, secluded harborage areas, e.g., under cupboards, behind cabinets, in wall voids, and around motor housings in appliances where they spend 75% of their time. At most, only one third of the population forages at night. Observation of foraging cockroaches congregate in harborage sites; but as the population increases, over crowding forces some of them to relocate.