Another class of Arthropods is the Diplopoda -- the millipedes. The body organization of the Diplopoda consists of a head and a many-segmented trunk. Each trunk segment bears two pair of segmented legs. Millipedes have one pair of antennae. Most species of millipedes are found in rotting logs, leaf litter, humus, and under stones where they feed on decaying vegetative material and fungi. They have numerous legs, which are close together and short, locomotion is relatively slow and occurs by waves of leg movement down the trunk. When disturbed, millipedes often roll into tight coils. Many species secrete fluids such as hydrogen cyanide to deter predators.