Every fall, we get numerous reports of structures being invaded by large numbers of small worm-like insects. As it turns out, the invaders are actually millipedes, which aren’t insects. Millipedes have four legs per body segment, and the common one-inch long millipede has 160 legs total. Insects, on the other hand, only have six legs total. The most commonly observed millipede we hear about is approximately one inch long and very dark brown in color (Figure 1). The millipedes will often curl up when disturbed or dead (Figure 2).
Figure 2. Millipedes found dead inside a home.
Although large numbers of millipedes might seem like a bad thing, they are actually harmless. Millipedes neither bite or sting, and they don’t feed on structures, plants, or items in the home. When found indoors, they are considered accidental invaders as they are not able to reproduce indoors and will eventually die. These small millipedes feed on decaying plant material, and are considered beneficial organisms because they recycle organic matter. Typically, millipedes are found outdoors in damp areas where decaying material is available. During the spring and fall, millipedes often migrate in search of new feeding sites. Unlike other home invading pests, millipedes wander aimlessly without searching for anything in particular. When they accidentally find their way into sheds, garages, or homes they eventually dry out from lack of moisture. They are most commonly found in dark corners of the basement where they were trying to hide from light.
Millipede management isn’t normally feasible. The best strategy is to ensure that structures are properly sealed and any dead millipedes are swept or vacuumed up. Sources of millipede migrations can include long-term mulch piles, wooded areas, or non-managed grassy areas. Millipedes can travel as far as 50 feet or more. For this reason, insecticide sprays have limited effectiveness and aren’t recommended to reduce millipede populations.