Most millipedes are brown or black, but some species are orange or red. They range in size from 5/8-inch to 4-inches in length. There are many species of millipedes, most of which are long, cylindrical, many segmented, worm-like creatures. However, a few millipedes appear to be flattened. Every millipede has two pairs of legs attached to each apparent body segment.
Females lay 20 to 300 eggs in nests in the soil. The eggs hatch after several weeks. The young initially have only three pairs of legs and seven segments. They undergo a series of seven to ten molts during which the number of legs and segments increase. Many species reach sexual maturity in tow years, but some require four or five years to complete development. Adults can live several years. Most species over winter as adults or young.
Millipedes are found outdoors in situations where there is moisture and decaying organic matter, such as under trash, grass clippings, mulch, rotting firewood, leaf litter, etc. They can build up tremendous populations in forest litter and compost heaps. Millipedes become structural pests when they invade homes and other structures, sometimes in staggering numbers. This occurs when standing water in their natural habitat forces them out. Indoor movement is also caused by drought and their natural habitat forces them out. Indoor movement is also caused by drought and their natural migratory and mating instincts in the fall. Millipedes usually die within a few days of entering a structure unless there is a source of high moisture and a food supply.
Millipedes are active at night. They scavenge feeding on decaying organic matter. Most species produce a foul smelling fluid that comes out the sides of their bodies and is toxic to some insects and small animals. This substance can cause blisters on human skin.