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Cockroaches vary in size and coloration, but some species, at least at first glance, look just others. With the right knowledge and a close inspection, you may be able to determine not just cockroach species but cockroach gender: Depending on species, roaches can display instantly recognizable gender differences. Knowing gender is useful whether you’re keeping roaches as pets or assessing a pest problem.
Some roach species are totally wingless, such as the wingless cockroach (Calolampra elegans), native to Australia. But in other species, wings are a significant gender marker. For example, female oriental cockroaches (Blatta orientalis) are wingless while the males have wings spanning three-quarters of their body length. Pest control company Orkin cites the presence of wings as the primary gender identifier in this species. The Cuban burrowing cockroach is another species whose wings are gender identifiers: Both genders possess wings, but the female’s are markedly less developed.
In most cases, the female is larger than the male. The difference in size varies according to species -- in most cases, it’ll be necessary to see two specimens of different gender side by side to tell the difference, unless you’re an expert.
An Obvious Distinction
The Madagascar hissing cockroach (Gromphadorhina portentosa), is one of the largest species of cockroach in the world. This species has two important gender identifiers. Unusual for roaches, the male is larger than the female. The male is noted for his thorny protrusions, located just behind the head. Females possess only small bumps in the area.
Working on His Tan
Some species of roach display minor and subtle color variations between genders. The most distinct example of this variation exists in the Pennsylvania wood cockroach (Parcoblatta pennsylvanica). The males are a distinctive tan color; the females are a darker brown.
Hanging With His Buddies
The gender of a Pennsylvania wood cockroach can be determined without close inspection. Males are capable of flight, while females are flightless. Another important behavioral difference in this species is that males typically congregate with other males, while females are solitary.
Fat Bottomed Girls
As well as size, females and males may be distinguished by subtle differences in body shape. For example, male German cockroaches (Blattella germanica) have thinner, tapered bodies than the females, which are stout, with rounded bottoms.
Invisible Gender Marker
One key difference between cockroach genders that will not be obvious to the casual observer is the production of pheromones. Although we can’t detect the pheromone with our noses, they can be crucial to the control of pest roach species. A Cornell University study, "Identification of the Sex Pheromone of the German Cockroach, Blattella Germanica," found that female sex pheromones could be used to attract and trap males, significantly reducing the number of pest populations.
- Queensland Government; Department of Agriculture, Fisheries and Forestry: Wingless Cockroaches
- Orkin: Oriental Cockroaches
- Blattodea: Species File
- Orkin: What Does a Cockroach Look Like?
- University of Kentucky; Department of Agriculture, Food and Environment
- Penn State; College of Agricultural Sciences: Pennsylvania Wood Cockroaches
- University of Florida: German Cockroach
- Science Mag: Identification of the Sex Pheromone of the German Cockroach, Blattella Germanica
- Brand X Pictures/Stockbyte/Getty Images