German Cockroaches
Order:
Blattodea
Family: Blattidae
Scientific Name: Blattella germanica
The German cockroach, which
has worldwide distribution, is by far the most important and the most
common cockroach. In addition
to being a nuisance, it is associated with outbreaks of illness, allergic
reactions in many people, and transmission of a variety of pathogenic
organisms including at least one parasitic protozoan.
Biology and Habits
Adults are ½ to 5/8 inch (13 to 16 mm) long. They are light brown to tan except for two dark, almost parallel longitudinal stripes on their pronotal shield. The female is darker than the male, and her abdomen is broader. Adults rarely “fly.”
First and second nymphal instars have a dark brown to black thorax with pale lateral margins. The second and third thoracic segments are pale white centrally but have a continuous dark stripe near each margin. Later instars have two dark longitudinal stripes on the pronotum which continue down the dark abdomen. The yellowish-brown ootheca (egg case), carried by the female, is dropped immediately prior to egg hatch. It is ¼ to 3/8 inch (6 to 9 mm) long and is slightly arched. On the average, the female will produce about five oothecae, averaging 30 to 40 eggs each.
Developmental time (egg to adult) varies from 54 to 215 days, averaging about 103 days. There are usually three to four generations per year, and can be up to six. Adults live 100 to 200 days. Established German cockroach populations are typically composted of 75 percent nymphs.
German cockroaches are found throughout structures but show a preference for warm (70 degrees F/21 degrees C) and humid places. They are often found in kitchens, bathrooms and other rooms where people eat or drink. Any crack or crevice located near a source of food or water is prime harborage, and they spend about 75 percent of their time in such harborages. Small-sized instar nymphs require a tiny crack of 1/64 inch (1 mm), whereas the larger adults require a crack of 3/16 inch (5 mm) in width.
These cockroaches are most commonly introduced into buildings through paper products and packaging such as grocery bags, cardboard boxes and drink cartons, and through secondhand appliances such as refrigerators, TVs, VCRs, and microwaves. On rare occasions, they have been observed migrating from building to building on warm evenings. Although uncommon, they can survive outdoors during the warm months.
They feed on almost anything with nutritive value including all kinds of food, as well as soap, glue and toothpaste.
Activity periods vary with
life stage, age and physiological state.
For instance, reproducing females are quite active, whereas gravid
(with ootheca) females are relatively inactive.
Males spend most of their time in harborage.
All nymphs become immobile and stay in harborage during the last
three days of each instar while they prepare to molt.
Hence, nymphs spend about 30 percent of their developmental time
in areas not visible to the inspector.
Control
Follow the standard control procedures for cockroaches but more frequent service might be required because of their rapid reproductive rate. At least 85 percent of the population must be eliminated during the clean-out service, or the maintenance program might fail.
(Courtesy of the National Pest Control Association.)