Egg: Females of the
American cockroach lay their eggs in a hardened, purse-shaped egg case called
an OOTHECA. About one week after mating, the female produce an ootheca and at
the peak of her reproductive period, she may form about two ootheca per week
(Bell and Adiyodi 1981). The females on average produce an egg case about once
a month for ten months laying 16 eggs per egg case. The female deposits the
ootheca near a source of food by either simply dropping it or gluing it to a
surface with a secretion from her mouth. The deposited ootheca contains water
sufficient for the eggs to develop without receiving additional water from the
substrate (Bell and Adiyodi 1981).
The egg case is brown when
deposited, and turn black in a day or two. A typical egg case contains about
14-16 eggs. It is about 8mm long and 5mm high.
Larva on Nymph: the nymphal stage
begins when the egg hatches and ends with the emergence of the adult. The
number of times an American cockroach molts varies from 6-14(Bell and Adiyodi
1981). The first instars American cockroach is white immediately after hatching
then become greenish-brown. After molting instars of the cockroach nymphs are
white and then become a uniformly reddish-brown with the posterior margins of
the thoracic and abdominal segments being a darker color.
Wings are not present in the nymphal
stages and wig pads become noticeable in the third or fourth instars. Complete
development from egg to adult is about 600days.
The nymphs as well as the adults
actively forage for food and water.
Adult: The adult
American cockroach is reddish-brown in appearance with a pale-brown or yellow
band around the edge of the pronotum.
The males are
longer than the females because their wings extend 4mm to 8mm beyond the tip of
the abdomen. Males and females have a
pair of slender, jointed cerci at the tip of the abdomen. The male cockroaches
have cerci with 18 to 19 segments. The male American cockroaches have pair
styli between the cerci while the female do not.
LIFE CYCLE
The American cockroach has three
life stages. The egg, a variable number of nymphal instars and adult. The life
cycle from egg to adult averages about 600days while the adult life span may be
another 400days. The immature emerges from the egg case in about 6-8 weeks and
matures in about 6-12 months. Adults can live up to one year and an adult
female will produce an average of 150 young in her life time. Environmental
factors such as temperature and humidity can increase or decrease the
developmental time of the American cockroach. Outdoors the female shows a
preference for moist, concealed oviposition site (Bell and Adiyodi 1981).