If you spot what appears to be a gray and brown cockroach, you're probably looking at an American cockroach (Periplaneta americana), but in nymph form. Cockroaches on the whole can be a number of diverse colors, including reddish-orange, beige, black, brown and even light green. Young American cockroaches, however, are a mix of gray and brown.
Nymphs closely resemble adult American cockroaches, although they lack wings and are not as big. They begin their lives with bodies that are a blend of gray and brown elements, although that changes relatively quickly. The visual impression that nymphs give is an overall darker one when compared to adults. Once the nymphs have undergone molting several times, they transition into a markedly different reddish-brown coloring. American cockroaches can remain nymphs from anywhere between 160 and 971 days. As full-fledged adults, female American cockroaches sometimes survive for a maximum of 15 months. The males generally have briefer lifespans.
Once American cockroaches are mature, they stay reddish-brown for life -- no more gray. Adult American cockroaches also feature some light yellow or light brown elements on their thoraxes, specifically on the outer portions. Adult individuals of both sexes are equipped with wings, and their bodies are usually somewhere between 1 and 1.5 inches in length.
Gray and brown nymphs don't usually differ much from adult specimens as far as indoor preferences go. Like adult American cockroaches, the little guys are drawn to wet, moist and dim parts of indoor structures, including basements, attics and bathrooms. They're also commonly found near trashcans, which contribute to their rather yucky public images. If you see an insect rapidly scurrying away from the light into a big laundry basket that's holding your sweaty gym clothes, it might be an American cockroach, either young or mature.
If an American cockroach nymph is particularly big in size, he might not be fully gray and brown. Bigger nymphs tend to possess conspicuous yellow coloration over their belly areas. Smaller nymphs are more uniform color-wise.
Where These Cockroaches Live
American cockroaches have misleading common monikers, as they actually originated in Africa rather than in America. They presently live all around the planet. Just as American cockroaches are not choosy about food, they're not choosy about places to live, either.
- The University of Maine Extension: Cockroaches
- Penn State Entomology: American Cockroaches
- University of Florida IFAS: American Cockroach
- Texas A&M AgriLife Extension: American Cockroach
- Michigan State University Diagnostic Services: American Cockroach
- Virginia Cooperative Extension: American Cockroach
- University of Michigan Animal Diversity Web: Periplaneta Americana
- Clemson University Entomology, Soils and Plant Sciences: Understanding Cockroach Control
- Texas A&M AgriLife Extension: Cockroach Biology and Management
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