The Life Cycle of Roaches
The eggs of the American cockroach sit inside of a dark shell-like casing known as an ootheca. Each ootheca can hold 16 eggs and females can produce up to two oothecas in a single week when at her most fertile. On average, females produce 10 ootheca a year, totaling roughly 160 offspring.
The German cockroach produces more eggs per egg capsule than any other common roach species. Each ootheca contains between 30 to 50 eggs and the female carries the capsule until it hatches roughly 28 days later. In a lifetime, a female will produce roughly 6 to 8 oothecas.
The oothecas of Oriental roaches are dark, smooth, and large. Each ootheca contains roughly 16 eggs and females produce 8 capsules on average throughout their lives. The female carries the ootheca anywhere between 12 hours to 5 days before selecting a sheltered, warm area for it to hatch, at which time the female more or less abandons her offspring.
This stage begins at the moment of hatching and extends until the adolescent roach matures into adulthood. During this period of time, the roaches go through several molting periods called instars. The first instar, when hatched, is whitish/grey in color and with each progressive instar, the roach adapts the more reddish-brown coloration of the adult. These nymphs begin without wings and start developing wing pads during their 3rd or 4th instars. In total, American cockroach nymphs will go through between 6 and 14 instars before reaching adulthood.
This stage lasts for 42 to 217 days (6 to 31 weeks), in which the young roach will progress through 6 to 7 instars. The nymphs are darker in color than the adults and tend to have a light streak of brown down the center of their backs.
The nymphs of Oriental roaches are shockingly light in comparison to the adults. They are reddish-brown, lack wings, and go through 7 molting periods prior to reaching adulthood. Their progression through the 7 instars lasts roughly 1 year in which the roaches will grow and darken to the familiar look of the Oriental roach.
On average, American cockroaches are 4cm in length and have reddish-brown bodies. The adults have the capability of flying with their fully formed wings and prefer to inhabit warm, moist places.
Adult German cockroaches measure on average 12.7cm to 15.8cm in length. They are light brown with two dark bands on their heads and tan-colored wings. Out of all species of roaches, the German roach has the greatest reproductive potential, producing up to 400 offspring in their super short lifetimes.
The female oriental roach is somewhat similar in stature to the later instars of the nymph – short and with rudimentary wings. The males have fully developed wings, but they are notably shorter than the full length of their bodies. They are both very dark brown/black in color and range from 1 to 1¼ inches in length.
Total Life Cycles
The life expectancies of cockroaches can vary drastically depending on the specific sub-species of roach. For American cockroaches, maturing from egg to adult takes on average 600 days (20 months). Following that, the adults live for roughly another 400 days (13 months), resulting in a total lifespan of about 2-3 years.
German cockroaches have different lifespans depending on their gender. Males live between 100 to 150 days (3-5 months), while the females live on average 190 to 200 days (6-6.5 months). These life spans are far shorter than those of both the American cockroach and the Oriental cockroach.
The incubation period for the Oriental cockroach lasts between 42 to 81 days (1-2.5 months), following which the hatched nymph progresses into adulthood in roughly 365 days (12 months). The adults live for a surprisingly short period of time, only lasting between 34 to 180 days (1-6 months). In total their lifespans last about 1 to 2 years.
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Hahn, J. and Ascerno, M. (2018) Cockroaches, The University of Minnesota Extension. Available at: https://extension.umn.edu/insects-infest-homes/cockroaches#american-cockroach-137713 (Accessed: August 2020).
McCanless, K. (2017) Oriental Cockroach, The University of Florida. The Florida Department of Agriculture and Consumer Services. Available at: http://entnemdept.ufl.edu/creatures/urban/roaches/oriental_cockroach.htm (Accessed: August 2020).