The head bears a pair of antennae, a pair of mandibles, and a pair of fused first maxillae. There is no second maxilla and its somite is absent. The heart is an elongate osyiate dorsal tube extending most of the length of the body. The nervous system consists of a three-part uniramian brain and a double, ganglionated, ventral longitudinal nerve cord. Excretion is accomplished via a single pair of Malphigian tubules and a pair of maxillary glands.
Respiration is via segmentally arranged trachea with segmental spiracles.
Milipedes are dioecious with the gonopores between somites 2 and 3. Juveniles hatch with three pairs of legs and add body segments and additional legs with succesive molts. The gut consists of foregut, midgut, and hindgut and runs the length of the body. The exoskeleton is strengthened with calcium salts and is correspondingly harder than that of most uniramians. Living millipedes can be anesthetized or killed by exposure to ethyl acetate fumes.