Blattella germanica

roach Appearance

Adult German cockroaches are approximately 1/2 half inch long. Males are grayish-tan with two black stripes on the pronotum, and have a tapering abdomen. Females are usually darker and their abdomens are more rounded. Nymphs are quite different in appearance than the adults. After molting, they will be ivory white for several hours before turning dark.

The German cockroach causes the greatest number of requests for pest control and boasts the highest number of control failures of any household pest. roachAdult female
1/2 to5/8 inch

Life Cycle

Eggs. The egg capsule of the German cockroach is about 1/4 inch long. Each egg capsule contains 30-40 eggs. Altogether, the female will produce from four to eight capsules in her lifetime.

In all large infestations, there are egg capsules present. Even if the cockroach population is eliminated, as many as one in every twenty egg cases can still hatch.

Nymphs. The eggs hatch when the nymphs inside create pressure that splits the case and allows the young to escape. As they develop, they molt six or seven times before reaching the adult stage. When molting, nymphs are very soft and vulnerable.

Adults. Adult cockroaches emerge from the last nymph as molt, fully winged. They join a nearby aggregation made up of other adults and larger nymphs.

Behavior and Harborage

Cockroaches live in areas of high humidity and nearby food. They will find harborage into which they can fit closely. As the number of roaches increase and favorable harborage is filled, roaches are forced to leave the aggregation or remain in less favorable harborage. They will find these new sites during their foraging periods just before dawn and after dark.

Mating. Females do not respond to mating behavior for more than one week after becoming adult. Proximity for mating is especially important, as males and females have to touch antennae and exchange sex pheromones to initiate mating. After mating, females feed intensively for several days, then seek secure hiding places where they can be safe with their egg capsules.

Such seclusion means that females with egg capsules feed less frequently and are exposed to pesticides less often. Clients often report seeing no adult roaches after a technician's last treatment, but later observe "little black ones". The client is reporting the success of the females with egg capsules that were deep in harborage and did not come in contact with superficially or inexpertly applied pesticides.

Foraging. The foraging pattern of German cockroaches is much less random that one would expect. The roaches leave their refuge and usually go to the first perpendicular surface they find, where they stop, turn, and move along the intersection of the two surfaces (usually a floor and a wall). As one can imagine, food crumbs often wind up in the same places, that is in wall moldings, corners made by walls, stoves, counters, canisters, etc.

The most convenient hiding places, in and around refrigerators, stoves, under sinks, and undisturbed cabinets, provide both protection and food. The most favorable humidity level is found in kitchens with sink traps, leaking faucets, standing water, wet sponges, etc. A bathroom is popular because of its toilet bowls, sinks, wet wash cloths, and sometimes, water heaters. While there is less food in bathrooms, food areas are usually nearby or available through holes around plumbing pipes. These pipes provide additional refuge and areas for population expansions into adjacent rooms or apartments.

In areas of great infestation, German cockroaches can build up outside heavily infested apartment units in the summer. Most often, outdoor infestations are found only outside the structures from which steady roachroach migrations occur and near dumpsters and garbage cans.

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