The crawling creatures called centipedes and millipedes are members of the same animal group—the arthropods—that includes insects, spiders, and crustaceans. Like the other arthropods, they have hard coverings on the outside of their bodies. Unlike the others, they have many body segments and sometimes hundreds of legs. There are more than 2,500 different species, or kinds, of centipedes and 10,000 species of millipedes.

Where centipedes and millipedes live

Centipedes and millipedes are found all over the world, but they are most common in the tropics. Most types like dark, moist places, though some millipedes can live in deserts. They spend most of their time in the soil, under stones, or in rotting leaves or wood. Some live in caves. The house centipede of North America and Europe is unusual because it lives in buildings.

Physical features

Centipedes and millipedes have long, thin bodies that are divided into segments. The bodies of centipedes are flattened, while those of millipedes are rounded. They are usually reddish brown to dark brown. Centipedes and millipedes range in length from just ¹/₁₂ inch (2 millimeters) to 12 inches (30 centimeters). Millipedes are generally smaller.

In a centipede, every body segment except the head and the rear has one pair of legs. “Centipede” means “hundred-footed,” but not all species live up to the name. Centipedes may have as few as 14 or as many as 177 pairs of legs. The head has a pair of long antennae. Just behind the head is a pair of strong claws that contain poison.

In a millipede, the first body segment is legless and the next three have only one pair of legs. Otherwise, every body segment has two pairs of legs. “Millipede” means “thousand-footed,” but no millipede has more than about 200 pairs of legs.

Behavior

Centipedes hide during the day and come out at night to hunt. Most types are very fast on their feet. Centipedes usually eat insects, spiders, and other centipedes, but the largest ones can kill small mammals, birds, or reptiles. Centipedes kill their prey with their poison claws. Even a small centipede, such as the house centipede, can deliver a painful bite.

Millipedes are less fearsome than centipedes. Instead of hunting, they eat rotting plant matter. Some eat the roots of living plants. Millipedes move more slowly than centipedes and are armed for defense rather than attack. Some types have special glands that produce a smelly or poisonous liquid or gas. Others curl up into a ball and rely on their thick outer covering for protection.

Life cycle

Female centipedes and millipedes usually lay eggs in the soil. Some kinds of centipedes hatch with a complete set of body segments and legs. Others add segments and legs each time they molt, or shed their outer covering. Young millipedes have only a few body segments. They add more body segments and legs with each molting. Some centipedes can live for up to six years. Some millipedes can live 10 years.