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Cockroach Identification
- It helps to know what you're looking for -
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Summary: Cockroaches develop from eggs that are protected inside distinctive egg cases. Immature cockroaches resemble adults but lack wings. The main pest species of peridomestic* cockroaches differ in both size and color pattern.
Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)
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 There are many species of cockroaches but only a few are commonly found in association with people (peridomestic*). The species that do share our living spaces can be severe pests. Since your control options can vary depending on which cockroach species is present, correct identification is important.
Cockroach identification can sometimes be made on the basis of egg cases alone. In some pest species like the German cockroach the females carry the egg cases around until just before hatch, but other species, like the brownbanded cockroach, drop their egg cases (right) where they can be found during inspections.
*peridomestic = associated with human dwellings
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two brownbanded cockroach egg cases, egg capsules or "ootheca"; roughly 3/16" long (somewhat smaller than egg cases of the German cockroach); each contains numerous eggs
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What do cockroach eggs look like?
Cockroach eggs are normally tucked safely away inside an egg case, or "ootheca" (above). Each egg case contains multiple eggs lined up in two rows. The egg cases are so distinctive in shape and size that they can often be used to determine the extent and identity of an infestation.
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Eggs hatch in a few weeks and egg cases break open releasing the young nymphs. Cockroach nymphs look like a small version of the adults except they lack wing development (below).
Common Pest Species in US
German cockroach (Blattella germanica)
The German cockroach [picture] is relatively small, about 1/2"-5/8" (16 mm) long, brown in color with two dark stripes behind the head. The German cockroach is found worldwide in association with human dwellings (peridomestic).This species may be the one most frequently found infesting homes, apartments, restaurants, and any other place where food is handled.
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German cockroach nymph (note lack of wing development).
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Brownbanded cockroach (Supella longipalpa)
The brownbanded cockroach is relatively small like the German cockroach (less than 5/8" long) but lacks the stripes behind the head and is more oval (wider) in shape when viewed from above.
American cockroach (Periplaneta americana)
The American cockroach [picture] is considerably larger than the other two common pest species at about 1-1/2" (38 mm) long. This cockroach is reddish brown in color. Both German and American cockroaches can co-exist together in the same structure.
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