Carpet Beetles Are Often Mistaken For Nuisance Duff Millipedes That Invade Homes In Tremendous Numbers In Response To Bouts Of Excessively Dry And Hot Weather

The insects commonly known as “duff millipedes” belong to the genus Polyxenus, which includes a little more than 30 species worldwide, a few of which are common nuisance pests within homes and buildings in the United States. Tan to dark brown duff millipedes are extremely small at only 1 millimeter in length, but they are easy to distinguish from other millipedes due to the golden-brown bands of hair that wrap around their uncharacteristically short and stocky body.

Duff millipedes are frequently mistaken for carpet beetles of the genus Trogoderma when they are encountered within homes. However, Trogoderma beetles are larger in size at 2 to 5 millimeters, and their bodies are noticeably more elongated than those of duff millipedes. Also, unlike carpet beetles, duff millipedes tend to abruptly appear near tubs, sinks, bathroom and kitchen walls, and other indoor areas where moisture content is relatively high. The duff millipede pest species that frequently appears in moderate to large numbers within homes and buildings in Massachusetts is commonly known as the “pin cushion millipede” (Polyxenus lagurus).

The pin cushion millipede is particularly abundant in northeastern forested areas where they naturally dwell, and indoor invasions are common in homes located near wooded areas. Although duff millipedes are very common indoor pests, extension entomologists in the northeast claim that they are one of the most queried groups of insect pests among residential homeowners. Duff millipedes are rarely encountered outdoors due to their preference for establishing harborages in protected locations, such as behind bark and within leaf litter.

Unlike most millipedes that secrete defensive fluids and possess a hard exterior, duff millipedes are soft-bodied and they rely solely on spines that protrude from their abdomen. Duff millipedes are known for migrating indoors in massive numbers to secure moist living conditions in response to bouts of excessive dryness and heat. Sealing crack, crevices and other potentially entry points of the exterior walls of homes, controlling indoor moisture, and keeping lawns well groomed will greatly reduce the chances of duff millipede invasions into homes.

Have you ever encountered duff millipedes indoors?