Class Diplopoda consists of millipedes. Millipedes have a head with one pair of antennae and a trunk with many segments, each of which bears two pairs of legs. They have numerous legs, often short positioned close together, so that locomotion is slow and occurs by waves of leg movement along the trunk. They also have the ability to roll their bodies into tight coils if they are disturbed. Millipedes live outdoors in damp areas such as under leaves and dead plant debris or in cracks and crevices. They feed on damp and decaying vegetable matter and are beneficial as "recyclers" of organic matter.