Millipede, any of about 1000 species of cylindrical, many-legged arthropods (see Arthropod). Found worldwide, millipedes have segmented bodies with two pairs of legs on each of the 9 to 100 or more abdominal segments, depending on the species, and one pair on three of the four thoracic segments. Because of their numerous legs, the animals walk slowly, with a wavelike motion of the legs down the body. In length they range from about 0.2 to 23 cm (about 0.1 to 9 in); the largest North American species may reach a length of 10 cm (4 in). Millipedes have a hard protective layer of calcium-containing chitin (except in some small species), two simple eyes, one pair of mandibles, two short antennae, and (in most species) stink glands with secretions that repel or kill insect predators. Another protective strategy is to curl into a spiral or a ball when threatened. The animals live in dark, damp places and feed on decaying plant life, sometimes damaging crops but also enriching the soil. They grow by molting and may live for one to seven years.

Scientific classification: Millipedes make up the class Diplopoda. The largest North American species is classified as Narceus americanus.