German Cockroach

Scientific Name: Blattella germanica (Linnaeus)
CLASS/ORDER/FAMILY: Insecta/Blattodea/Blattellidae
METAMORPHOSIS: Simple

Introduction:

The German cockroach is by far the most important and usually the most common of the cockroaches. In addition to being a nuisance, it has been implicated in outbreaks of illness, the transmission of a variety of pathogenic organisms including at least one parasitic protozoan, and allergic reactions in many people. This species has worldwide distribution.

Recognition

Adults about 1/2-5/8" (13-16 mm) long. Color light brown to tan except for 2 dark, almost parallel longitudinal stripes/bars/streaks on pronotal shield. Female darker than male, her abdomen broader. Rarely glide or "fly".

Nymphal instars 1-2 with thorax dark brown to black but having pale lateral margins, meso- and metathorax pale/white centrally but with a continuous dark stripe near each margin; thorax and abdomen light brown ventrally. Later instars (3rd on) with 2 dark longitudinal stripes on pronotum continuous with dark abdomen, and abdominal segments usually with central areas pale on dorsum.Ootheca or egg capsule yellowish brown but usually two-toned, paler end attached to female; about 1/4-3/8" (6-9 mm) long, with length more than twice width; subdivisional furrows extending entire width; slightly bowed or arched; and with about 15-20 (range 925) eggs on each side.

Similar Groups

(1) Asian cockroach (Blattella asahinai) with almost identical color pattern, attracted to lights, flies readily, breeds outdoors in leaf litter, presently known only from Florida, identification should be confirmed by an expert.

(2) Brownbanded cockroach (Supella longipalpa) and Pennsylvania wood cockroach (Parcoblatta pensylvanica) lack 2 dark longitudinal stripes on pronotal shield.

(3) Field cockroach (B. vaga) with a median dark line between eyes on front of head.

(4) Other cockroaches are either smaller or larger, lack characteristic pronotal stripes, and/or are not associated with structures.

Biology

The female carries her ootheca until it is within 1-2 days of hatching, and then deposits it in a sheltered area/site. On the average, the female will produce about 5 oothecae (range 4-8), averaging 30-40 eggs (range 18-50) each.Developmental time (egg to adult) usually varies from 54-215 days, averaging about 103 days; under lab conditions of 80 degrees F/27 degrees C and 40% relative humidity, usually only 50-60 days are required. This means usually 3 to 4 generations per year, but up to 6. Adults live about 100-200 days (range 1-303). Established/mature German cockroach populations are typically composed of at least 75% nymphs.

Female German cockroaches create egg pouches known as oothecae. These oothecae remain attached to the female’s abdomen until they are nearly ready to hatch.German cockroach nymphs resemble adults. However, nymphs are much smaller, do not have wings and are incapable of procreating. As they grow, nymphs shed their exoskeletons several times.

These nymphal stages span approximately 100 days. After the final molt, German cockroach nymphs are fully developed, winged adults equipped with reproductive capabilities.German cockroach nymphs are similar to the adults of their species. Often mistaken for albino cockroaches, newly molted individuals are white in color. However, the white cuticles covering their bodies gradually darken and harden. German cockroach nymphs may consume their cast-off skins as food. Eventually the nymphs will be dark brown or black in color and characterized by a single, light stripe that runs the length of the back.

Habits

German cockroaches are found throughout structures but show a preference for warm (70 degrees F/21 degrees C) and humid places. They are usually found in kitchens and secondarily in bathrooms, but infestations often occur in rooms where people eat and drink while watching television such as the den, bedroom, etc. Any crack or crevice located near a source of food and/or water is prime harborage, and they spend about 75% of their time in such harborages. First instar nymphs require a crack of about 1/32" (1 mm) whereas, adults require a crack of about 3/16" (5 mm) in width.

Signs of a German Cockroach Infestation

Droppings:German cockroach droppings may appear as small, dark, “pepper-like” material left on countertops or in drawers. Fecal staining may appear as dark spots or smears, some that are slightly raised, in the corners of rooms, along the tops of doors or around small cracks and openings into walls.

Egg Capsules:Since German cockroach females carries their egg case until 1 to 2 days before depositing it, empty egg cases may be found in areas that the females frequent.

Odor:German cockroaches are also known to secrete a number of odorous compounds. When populations are present in large numbers, it may be possible to detect a mild, or what some have reported as a “musty” odor.

Control

Follow the standard control procedures but more frequent service may be required because of their rapid reproductive rate. At least 95% of the population must be eliminated on the initial or clean-out service, or the typical maintenance program will usually fail. Baits are particularly effective, but correct placement along junctions and/or in cracks and crevices in or near harborages is essential. Incorporating IGRs (insect growth regulators) into the service helps with long-term control. Be sure to follow label directions.