Phylum: Arthropoda – insects, crustaceans, spiders, millipedes
Class: Insecta – insects
Order: Blattodea - cockroaches
Scientific Name: Gromphadorhina portentosa
Description: The MHC is a large, wingless cockroach. Like other cockroaches, their bodies are flattened, which allows them to crawl into narrow crevices. The head is small, and is usually held underneath the thorax (which can then be mistaken for the head). Adults are dark chocolate brown with dark orange markings on the abdomen. They can reach 4 inches in length. Males have a pair of large bumps behind their heads, which they use in territorial fights. Females have much smaller bumps, or none at all.
Home Range: Madagascar
Habitat Type: Tropical forests
Reproduction: Dominant males establish territories for breeding, and may mate with several females. Pairs communicate by hissing, or through postures and stereotyped movements. Pheromones may also be important. Courtship begins with both partners hissing and stroking each other with their antennae. Mating usually takes 20-30 minutes. This species is ovoviviparous – the eggs hatch within the female’s body, so that the female appears to give birth to live young. The eggs are actually laid in a purse-like capsule called an ootheca, which is divided into many compartments. Each compartment contains an egg. The ootheca remains in the body, in a special brood patch where the eggs are incubated. They hatch in approximately 60 days. A female can produce 20-60 nymphs in a clutch. Cockroaches exhibit “gradual metamorphosis” – eggs hatch into nymphs, which resemble miniature adults. Nymphs are born white, but become brown as they age. They will molt six times before reaching adult size. At each molt, the exoskeleton splits down the middle of the back, and the roach slowly wiggles its way out. Newly-molted roaches are white, and will gradually darken as the new skin hardens. This takes several hours. They reach maturity in five to ten months.
Diet in the Wild: MHC’s are scavengers, feeding mostly on rotting fruits that have fallen from trees.
Diet in the Zoo: In captivity, they eat almost any type of dry feed, such as dog food, iguana food, or rat chow, and produce such as celery, lettuce, carrots, bananas, apples.
General Information: MHC’s are known as “living fossils”, because they closely resemble the prehistoric cockroaches that lived 300 million years ago. Like most other cockroaches, they are most active at night. They do not fly, but can run quickly. They have special pads on their feet that allow them to climb almost any surface. Even so, they are usually found on the forest floor, living in rotten logs.
This species is best known for its ability to hiss. The hissing sound is produced by forcing air through a pair of modified spiracles on the abdomen. Air sacks in the body work like bellows to squeeze the air out. The hiss can be heard 12 feet away, and can startle a predator so that the cockroach has time to escape. The sound is one of their only defenses against predators, since they do not bite. Hissing is also important in courtship and fights between males, and several different hisses have been identified in different situations.
MHC’s usually live in colonies with a three-tiered social hierarchy. Dominant males are able to establish and defend territories around several females. They use the large bumps on the thorax to push out any intruding males. Fights are accompanied by loud hissing, and the largest male (who probably also has the loudest hiss) usually wins the fight. Males that are pushed out of territories become “satellite males”. They stay near the edges of a territory, sometimes fighting with the territory-holder or with other satellite males. If a dominant male is injured, or otherwise cannot keep his territory, one of these satellite males will take his place. Satellite males may breed with females, but not as often as the dominant male. On the lowest tier are the subordinate males. They do not fight, and they breed less than the dominant or satellite males. Females and nymphs do not fight, and they are free to enter and leave any territory.
Hissing cockroaches are an important part of the forest ecosystem – they play a large part in decomposing fruit and other rotting material on the forest floor, and they are an important food source for other animals.
Fun Facts about cockroaches in general:
● A cockroach can hold its breath for 40 minutes.
● A cockroach can live for a week without its head. It eventually dies of thirst because it can’t drink without a mouth.
● The blood of a cockroach is white.
● There are about 5,000 species of cockroaches – only about half a dozen are pests.
Conservation Status: MHC’s are not endangered. However, as an endemic species, they may be susceptible to habitat destruction on Madagascar.
Predators: Larger animals such as birds, lemurs, and lizards
The Encyclopedia of Insects. 1993. C. O’Toole. Facts on File Inc., New York. pp. 12-13, 32-33.
“Madagascan Giant Hissing Roaches”. L. Darmo and F. Ludwig. Carolina Biological Supply Company.
”Madagascar Hissing Cockroaches: Information and Care”. P. Mulder and M. Doss. Oklahoma Cooperative Extension Service.
“Paw-Prints.” Oct/Nov 2002. Wildlife Adventures Vol. 5/02, The National Zoo newsletter. P. 5
Zoofari News, Houston Zoological Gardens docent newsletter.