Madagascan hissing cockroach
Scientific Name: Gromphadorhina portentosa
Country: Madagascar
Continent: Africa
Diet: Rotting fruits, fungi
Food & feeding: Herbivore
Habitats: Tropical dry forest, tropical rainforest
Conservation status: Not Threatened
Relatives: Several thousand other species of cockroach, common in many parts of the world.
Description: There are about 3,500 different species of cockroach, which make up the insect order dictyoptera, along with the closely related praying mantis. This is a very ancient insect order, with fossilised cockroaches estimated to be 300 million years old! Hissing cockroaches live in the leaf litter of the forest floor in Madagascar. They do not have wings and their flattened shape lets them move easily amongst the leaves. They can grow to a length of about 9 cm. Insects are covered in a hard outer casing (the exoskeleton), which has a waterproof layer. To get air into their bodies they have a system of tubes that branch many times, getting ever smaller, to reach all parts of the body. A pair of openings, called spiracles, is found on each segment of the body. When alarmed, the hissing cockroach rapidly squeezes air out of the spiracles on the front segments of the abdomen, making a hissing sound which can be heard 12 feet away!
Lifestyle: As decomposers, they perform an important role in nature, and break down the decaying plant and animal matter. In the Zoo, they are offered a variety of fruit and vegetables, including tomato, lettuce, banana, orange and grapes. The enclosure is sprayed with 'reverse osmosis' water each day to maintain the appropriate humidity.
Family & friends: For an insect, hissing cockroaches have surprisingly advanced social lives. Once her eggs have hatched, a female will look after her young for several months. During this time, the young cockroaches may feed on her droppings, taking in vital micro-organisms that will help them digest the cellulose in their diet. Males are territorial.
Keeping in touch: As their name suggests, these cockroaches can hiss! Hissing serves three purposes. Males are strongly territorial and should they meet, they will engage in pushing fights, ramming each other with their hardened head shields, hissing as they fight. Males also hiss when courting females, although much more quietly than when they are fighting. Lastly, males will hiss very loudly when they are disturbed - perhaps this might startle a predator, giving themselves a chance to escape.
Growing up: Female cockroaches lay their eggs in a neat array and surround them with a frothy substance that hardens as it dries. This protective structure is called an ootheca and kept within the body cavity of the female for about two weeks, until the eggs hatch. The young nymphs are miniature versions of the adults but remain white until the outer cuticle hardens. The males of this species can be distinguished from the females by the 'horns' or raised bumps on the front of their heads. The hard outer covering (the exoskeleton) does not grow with the cockroach, so the nymph periodically develops a new covering underneath the old, which then splits and is shed. The new covering is soft and white and allows the nymph's body to grow, before hardening and darkening in colour. The final moult takes place when the insect is about 9 months old, after which it becomes sexually mature.
Cockroaches, in general, are almost indestructible. Some can survive freezing for two days, go without food for three months or live through a dose of radiation 100 times that which would kill a human! They have adapted to many different habitats worldwide and will eat almost anything.
Conservation news: They are not threatened at the moment. Hissing cockroaches are important nutrient-recyclers in the Madagascan forests. The dry forests in which they live are amongst the most threatened of all the habitats in Madagascar, due to slash-and-burn agriculture and mining activities.
