Adult females lay up to a few hundred eggs in soil, leaf litter, etc., and the immatures pass through a series of molts, gradually increasing in size. Millipedes often leave their natural habitats at night and crawl about over sidewalks, patios, and foundations. At certain times of the year, especially during autumn, they may migrate into buildings in great numbers. Fall movement into structures appears to be accidental, occurring in the course of searching for humid overwintering sites. Migration into buildings also is common during spring and summer, in conjunction with periods of excessively wet or dry weather.
Millipedes often invade crawl spaces, damp basements and first floors of houses at ground level.
Frequent sightings of these pests indoors usually means that there are large numbers breeding on the outside in the lawn, or beneath mulch, leaf litter or debris close to the foundation. Because of their moisture requirement, they do not survive indoors more than a few days unless there are very moist or damp conditions. Leaves, grass clippings, heavy accumulations of mulch, boards, stones, boxes, and similar items laying on the ground beside the foundation should be removed, since these often attract and harbor pests. Items that cannot be removed should be elevated off the ground. Don't allow water to accumulate near the foundation or in the crawl space.