Common Name: German cockroach
Scientific Name: Blattella germanica (Linnaeus)
Description: The adult German cockroach is about 5/8 inch long, overall light brown in color and wings which cover the abdomen. The thoracic shield just behind the head (pronotum) is marked with two prominent black stripes. Immature stages (nymphs) are smaller, wingless and have a pale stripe (on at least the second and third thoracic segments in first stage nymphs) running lengthwise down the middle of the darker brown body.
The field cockroach, Blattella vaga Hebard, is similar to the German cockroach in appearance, but it occurs primarily outdoors where it feeds on decaying plant materials. Compared to the German cockroach, it is more active during daylight hours and will be found around lights. They also are known to fly when disturbed. The brownbanded cockroach, Supella longipalpa (Fabricius) is about the same size as the German cockroach, but appear ” banded” because the wings are marked with a pale brown band at the base and another about a third of the distance from the base.
Life Cycle: Simple metamorphosis. Mated females produce an egg capsule that is attached to the end of the abdomen for up to a month before being dropped a day or so before eggs hatch. Each 5/16 inch long, brown egg capsule contains 30 to 40 eggs which hatch in 2 to 4 days after being deposited. Nymphs hatching from eggs are less than 1/8 inch long and wingless. They develop through 6 to 7 stages (instars) over 74 to 85 days (varying with temperature) before becoming adults. There may be four generations per year.
Habitat, Food Source(s), Damage: This is mainly an indoor species although they will also migrate outdoors from structure to structure. Occasionally, new infestations begin by bringing in cartons and other materials from infested structures that harbor the roaches or their eggs. Kitchens, bathrooms and other locations that provide food, moisture, warmth and shelter are preferred habitats. German cockroaches are mainly active at night, when they search for food and water. During the day, they remain concealed in cracks and crevices unless they are over-crowded, with all developmental stages occurring together. They also can occur in attics, wall voids, crawl spaces, foundation cracks, garbage areas and around the landscape. May spread food contaminants. Some people have allergic reactions to cockroaches or cockroach residues (e.g., feces, body extracts).
Pest Status: One of the most common household cockroach pests in the state; presence in homes is a nuisance and they may spread food contaminants. Some people have allergic reactions to cockroaches or cockroach residues (e.g., feces, body extracts).
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Ebeling 1978; Hamman and Owens 1981; Olkowski et al. 1991.