Cockroaches: Blattodea

Most species are active at night, but some wild cockroaches are active during the day.

Many cockroaches burrow under the ground, beneath dead leaves, or in rotten wood to avoid danger or to rest. Cave-dwelling species burrow into piles of bat waste or slip into narrow cracks in rock walls. Some species run quickly or fly away to avoid danger. Others simply freeze with the approach of a predator. Many cockroaches have special organs in their bodies that make a variety of irritating chemicals that they spray from the tip of the abdomen at their attackers. Many larval cockroaches and some adults produce a glue from the abdomen, which sticks to the legs of ants and beetles, preventing them from attacking the cockroach.

When disturbed, many cockroaches can make sounds. Madagascan hissing cockroaches hiss by quickly blowing air out of breathing holes along the sides of their abdomens. In other species there is a rasp on the edge of the midsection. Next to the rasp is a thickened vein, or file, on the forewing. By rubbing these two structures together, the cockroach can make a faint rasping or squeaking sound.

Some cockroaches live in groups and provide care for their larvae. The rhino cockroach of Queensland, Australia, digs its burrow in sandy soil and builds an underground nest for its young, lining it with leaves, grass, and roots. Other species live in groups but do not care for their young. Still other cockroaches are loners, living mostly by themselves until it is time to mate.

Mates locate each other through pheromones (FEHR-uh-mohns), special chemicals released from the body that are especially attractive to members of the opposite sex of the same species. Eyesight plays little or no part in finding a mate or in courtship, despite the fact that most species have well-developed compound eyes. Many cockroaches engage in complex courtship dances. Females "call" males by raising their wings to expose special glands on the abdomen that release a pheromone to attract the male. Males have their own special organs on their backs that the female either eats or licks during mating. Other species show little or no courting activity before mating. During mating the male transfers his sperm packet directly into the reproductive organs of the female.

Nearly all female cockroaches put their eggs in a pillow-like capsule. Each capsule may have just a few to nearly 250 eggs, aligned in two rows. In some species the female carries the egg capsule on the tip of her abdomen for several days or weeks and then later leaves or buries them near a good supply of food and water. Some species can draw the capsule into the abdomen for short periods of time, to protect it. In other species, the capsule is kept in the abdomen until the eggs hatch inside the mother. The larvae are then "born" as they leave the mother's body. A few Australian cockroaches do not produce an egg capsule, but the eggs are kept inside the body. Only one species, Diploptera punctata, gives birth to live young. Its eggs are kept inside the body without a capsule and are nourished, or fed, by the mother's body until they are born. Most cockroaches never see their young. But in some species the larvae gather in a group under the mother, where they remain for a short period of time. Among some cockroaches the larvae spend their first days in a special chamber under the mother's wings.