The Madagascar Cockroach
The Madagascar hissing cockroach (Gromphadorhina portentosa), also known as the hissing cockroach or simply hisser, is one of the largest species of cockroach, reaching 2 to 3 inches (5.1–7.6 cm) at maturity. They are native to the island of Madagascar, which is off the African mainland, where they are known to be found inside of rotting logs. It is one of some 20 known species of large hissing roaches from Madagascar, many of which are kept as pets, and often confused with one another by pet dealers; in particular, G. portentosa is commonly confused with G. oblongonota and G. picea.
Unlike most cockroaches, they are wingless. They are excellent climbers and can scale smooth glass. Males can be distinguished from females by their thicker, hairier antennae and the very pronounced "horns" on the pronotum. Females carry the ootheca internally, and release the young nymphs only after her offspring have emerged within her. As in some other wood-inhabiting roaches, the parents and offspring will commonly remain in close physical contact for extended periods of time. In captivity, these insects have been known to live up to 5 years. They feed primarily on vegetable material.
Hissing
As the common name suggests, the Madagascar hissing cockroach is characterized by their hissing sound, which is produced when they forcefully expel air through the specially-adapted respiratory openings (spiracles) on the fourth segment of their body, though spiracles are found on all segments of their abdomen. The Madagascar hissing cockroach is only one member of a group of roaches that can hiss; this exact mode of sound production is atypical, as most insects that make sound do so by rubbing together various body parts ("stridulation"), such as legs. Some long-horned beetles, e.g., the giant Fijian long-horned beetle, hiss by squeezing air out from under their elytra, but this does not involve the spiracles. In hissing roaches, the hiss takes three forms: the disturbance hiss, the female-attracting hiss, and the aggressive fighting hiss. All cockroaches from the fourth instar (fourth molting cycle) and older are capable of the disturbance hiss. Only males use the female-attracting hiss and fighting hiss; the latter is used when challenged by other males (males will establish a dominance hierarchy, and a submissive male will back down to end a fight). The hissing makes them a popular pet.
Associations with other animals
The mite species Gromphadorholaelaps schaeferi lives on this species of cockroach along the undersides and bases of the legs and takes some of its host's food as well as consuming particulates along the host's body. As these mites do not harm the cockroaches they live upon, they are commensals, not parasites, unless they build up to abnormal levels and start starving their host. Recent studies have shown that these mites also may have beneficial qualities for the cockroaches, in that they clean the surfaces of the cockroaches of pathogenic mold spores, which in turn increases the life expectancy of the cockroaches.
Written By David Davidson
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