The Madagascar hissing cockroach (Gromphadorhina portentosa) is approximately 5 to 10 centimetres long and weighs 7 to 25 grams. The roach is heavily sclerotized, giving it a brownish or black colour over the entire body. Immediately after the molting process, the Madagascar hissing cockroach will exhibit a white colouration until the exoskeleton hardens. To avoid hurting the insect in this stage, the cockroach should not be handled during this time.
Unlike many other cockroaches, this species is wingless but can run rather quickly.
The male roach has two large tubercles (bumps) on the dorsal surface of the prothorax. At first glance, many people confuse these tubercles with eyes; however, the head is located underneath this area and is protected by the heavy armor of the prothorax.
The female Madagascar hissing cockroach also possesses these bumps; however, they are not as prominent and are rather smooth.
Both sexes possess a modified second abdominal spiracle (breathing port on the side of the body). By forcing air through these spiracles, they can produce a hissing sound during mating, fighting, or when they are disturbed.
The cockroaches are equipped with special pads on their feet that allow them to climb most surfaces, including glass.
The Madagascar hissing cockroach is one of the rare ovoviviparous species of roaches, producing eggs that hatch within the female’s body. This makes it appear that the female is giving birth to live young. After fertilization, the eggs are incubated by the female in a special brood pouch within her body.
The gestation period under laboratory conditions is about 60 days. The roach exhibits gradual metamorphosis (development as eggs, nymphs, and finally adults). The nymphs undergo six molts. It requires nearly five months (5-12 months depends on climate) for the roaches to become sexually mature.
Similar to other cockroaches, the Madagascar hissing cockroaches is negatively phototactic (moves away from light) and, therefore, is nocturnal in activity. The Madagascar hissing cockroaches is also omnivorous (eats anything), but is strongly attracted to peanut butter, bananas, and oranges.
When living in colonies, this species exhibits a definite social hierarchy. Males will establish and defend territory on a rock or other similar structure for several months. He will leave it only for brief periods to obtain food and water.
Female Madagascar hissing cockroach is gregarious (form groups) and has not been observed to fight either among themselves or with males. Females and nymphs are allowed on the defended area that may harbor several adult females and an assortment of various-sized nymphs, but only one male.
When a male intrudes on a neighboring male’s territory, a fight will ensue. One male will attempt to push the other out of his territory. During the battle, a great deal of movement and hissing will occur; however, no harm is done to the loser.
Mating behaviour of the Madagascar hissing cockroaches is elaborate and involves posturing and hissing by the males to attract females.