The Madagascar hissing cockroach (Gromphadorhina portentosa) is a popular pet insect. Known for their distinctive hissing sounds and large size (2 to 4 inches), these insects are native to Madagascar. While they may appear similar at first glance, observable characteristics allow for distinguishing between males and females. Understanding these differences provides insight into their biology and behavior.
Physical Distinctions
The most apparent physical difference between male and female Madagascar hissing cockroaches lies in the pronotal horns. Males have prominent, bumpy protrusions (horns or tubercles) on their pronotum, the shield-like segment behind their head. These structures contribute to their robust appearance.
In contrast, females have a smoother pronotum with small bumps in the same area. This makes the pronotal horns a reliable visual cue for sex identification. While both sexes measure 2 to 4 inches, males appear slightly larger and more heavily built than females.
Beyond the horns, subtle differences can be observed in their antennae and abdominal segments. Male antennae are thicker and hairier, especially near the base. Female antennae are smoother. Examining the underside of the abdomen reveals further distinctions: males have three smaller plates at the tail end, while females have a single, larger segment.
Behavioral Differences
Behavioral patterns offer additional clues for distinguishing male and female Madagascar hissing cockroaches. Both sexes are capable of producing hissing sounds by expelling air through specialized breathing passages called abdominal spiracles. However, the frequency and context of their hissing vary significantly between males and females.
Males hiss more frequently and for a broader range of reasons, including aggression, courtship, and as an alarm. They engage in “hissing battles” and physical confrontations, using their pronotal horns to ram and push other males to establish dominance or defend territory. Females primarily hiss as a defense mechanism or when disturbed. Females display more social and less aggressive behavior than males.
Male cockroaches also exhibit territoriality, selecting and defending areas like holes in logs or other structures within their habitat. They will actively chase or fight off intruding males from their chosen territory. During courtship, males perform specific rituals, including unique hisses and antennal movements aimed at attracting females. These courtship hisses differ from their aggression or alarm hisses.
Reproductive Roles
The distinct reproductive roles of male and female Madagascar hissing cockroaches underpin many of their physical and behavioral differences. Males play an active part in initiating courtship and competing for mates. They use specific acoustic signals, such as calling and courtship hisses, to attract and interact with females. Mating involves the male pushing his abdomen under the female’s body to connect.
Females carry the ootheca, or egg case, internally, a reproductive strategy known as ovoviviparity. This means the eggs hatch inside the female’s body, and she gives birth to live nymphs. The gestation period for females is approximately 60 days, after which they can produce a clutch of 30 to 60 nymphs. While maternal care is limited in insects, the female provides internal incubation and live birth, contributing directly to the survival of her offspring.