We receive countless calls every year about tiny caterpillar or worm like insects crawling along walls and window sills inside of homes. Due to their minuscule size of only about 1 mm as an adult, duff millipedes can be difficult to identify. Often mistaken for the much larger larval stage of dermestid (carpet bugs), duff millipedes have bands of hairs around their bodies and a prominent tuft of hairs that extend from the end of their abdomen. Lacking any kind of resemblance to their hardened millipede cousins, duff millipedes also lack the chemical defenses of most millipede species. Instead, the tuft of protruding hairs from their abdomen acts as their defense. The ends of the hairs are hooked and easily detach from the body of the duff millipede when attacked. The more a predator attempts to free themselves from the hairs, the more entangled they become. It is not uncommon for ants to die from attacks on duff millipedes.
Most commonly found in the pine forests of Colorado, duff millipedes are also found in many areas along the Front Range. Duff millipedes feed on algae, fungi and decaying matter, which may attribute to their tendency to congregate in moist areas. Hot, dry weather often coincides with duff millipede invasions into homes. Their sudden appearance and high numbers often cause alarm in homeowners; however, duff millipedes are not likely to cause any damage within the home. Breeding typically occurs in the spring and fall, creating spikes in activity during those times. Eggs are laid on a silken mat spun by the male. Females produce the eggs in a sticky mass that is guarded by protective body hairs. Duff millipedes experience seven immature stages, each resulting in a molt that will increase both their size and segmentation. These immature stages take roughly 10 months to complete before the young reach adult maturity. Adults have an approximately 3 month life span.
Insecticides appear to be ineffective in the control of duff millipedes at this time. Performing exclusion techniques around the home including caulking and sealing of cracks, crevices and other openings around the home will assist in preventing invasions. Decreasing humidity, repairing plumbing or faucet leaks and ensuring proper drainage of moisture around the foundation of the home can also be helpful in decreasing activity. Removal of perimeter barriers around the foundation that promote moisture retention should also be removed as well as leaf litter and other organic debris.