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 9- 25) eggs on each side.
SIMILAR GROUPS
(Adults only)
- 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.
- Brownbanded cockroach (Supella longipalpa) and
Pennsylvania wood cockroach (Parcoblatta pensylvanica) lack 2 dark longitudinal
stripes on pronotal shield.
- Field cockroach (B. vaga) with a median dark line
between eyes on front of head.
- 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
oothecas (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'F/27'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.
HABITS
German cockroaches are found throughout structures but show a preference for warm
(70'F/21'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" (I mm) whereas, adults
require a crack of about 3/16" (5 mm) in width.
These cockroaches are most
commonly introduced into buildings via paper products or paper packaging such as grocery
bags, cardboard boxes, drink cartons, and via secondhand appliances such as refrigerators,
televisions, VCR'S, microwaves, etc. They have been observed to migrate from building to
building on warm evenings, but this rarely occurs. Although uncommon, they can survive
outdoors during the warm months.
They feed on almost anything with
nutritive value including all kinds of food, and such things 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 starting about the 5th day
after mating and go only to food and water when necessary. Males spend most of their time
in harborage, even at night. All nymphs become immobile and stay in harborage during the
last 3 days of each instar while they prepare to molt. Hence, about 1/3 of the time the
cockroach nymphs will not be found or found exposed during an inspection.
