Millipedes (Class Diplopoda) are elongated arthropods with cylindrical bodies that have two pairs of legs for each one of their 20 to 100 or more body segments. These animals are herbivorous, slow and nonvenomous unlike the somewhat similar and related centipedes. Most millipedes eat decaying leaves and other dead plant matter.
This class of arthropods are thought to be among the first animals to colonize land during the Silurian geologic period. These early forms probably ate mosses and primitive vascular plants.
The millipede's most obvious feature is its large number of feet. In fact its name is a compound word formed from the Latin roots milli (thousand) and ped (foot). Despite their name, these creatures do not have a thousand legs, but some rare species are close enough with their amazing 750 legs. However, more common species have between 80 and 400.
Having very many short legs makes millipedes rather slow, but they are very powerful burrowers. Waving their body length and with the legs moving in a wavelike pattern, they easily force their way underground, head first. They also seem to have some engineering ability, reinforcing the tunnel by rearranging the particles around it.
Due to their lack of speed, millipedes' primary defense mechanism is to coil into a tight spiral - protecting their delicate legs inside their armored body exterior - whenever they feel threatened. Many species also emit a somewhat poisonous liquid secretion, through microscopic pores along the sides of their bodies, as a secondary defense. Some of these substances are acidic and can burn the exoskeleton of ants and other insect predators, and the skin and eyes of larger predators. As far as humans are concerned, this chemical brew is fairly harmless, although it should never be eaten or applied to the eyes. In other words, use caution when handling millipedes. Secondary defense is rarely used, and only if the millipede is dropped, pinched, or otherwise treated roughly.
Unlike their close relatives, centipedes (class Chilopoda), millipedes are not venomous and cannot cause harm with their bite. Since most millipedes are herbivorous, feeding on decaying vegetation, their jaws are simply not strong enough for munching on anything not already half rotten. They moisturize the food with secretions and then scrape it in with their jaws.