Adult millipedes overwinter in soil or under leaf litter and become active in the spring, at which time the mating process begins. Both male and female millipedes produce pheromones to locate suitable mates. Males also stridulate, or create sounds by rubbing their legs together, to attract females.
After locating and mating with a male, the female deposits her eggs in a cluster of soil or a prepared underground nest. The number of eggs varies by species, with environmental conditions and health of the female affecting the egg production rates of millipedes. Eggs hatch after a few weeks, and the emerging larvae appear like small adult millipedes except with only three pairs of legs. Over the course of two to five years, larvae undergo numerous molts in which the number of body segments and legs increases (two pairs of legs per body segment). Millipedes molt 7 to 10 times before reaching sexual maturity, which ceases development. After reaching adulthood, millipedes may live for several more years.