Every fall, specimens start appearing at local Extension offices. They could be called “worms,” “armyworms,” “wireworms,” or much worse, but the pest is always the same – millipedes.

Usually the complaint isn’t about just one millipede, but lots of them.

Millipedes are long, slender, wormlike animals with 4 legs on each of most body segments. With that said, the common, inchlong millipede found in most landscapes, has 160 legs. Most people don’t notice their legs because they are small and tucked beneath their body. What people do notice about millipedes is their size (1 to 1/14 inch) their color (very dark brown), their shiny, hard shell (crunchy), their long, cylindrical shape and their habit of curling into a coil when disturbed or when they are dead.

There is “good” news and “bad” news. Millipedes are harmless. They can’t bite or sting and they don’t feed on structures, furnishings or landscape plants. They do feed on damp and decaying plant material and are beneficial as “recyclers” of organic matter. They live outdoors in damp areas such as under leaves, plant debris, mulch and similar habitats. The bad news is millipedes often go on mass migrations, especially on humid, warm nights in the fall and spring, during which time they wander into garages, basements and other parts of the house. All millipedes found inside have strayed in by mistake and can’t reproduce indoors.

Millipedes are most active at night. They wander out from their damp hiding places and roam aimlessly, often covering large distances with their slow, steady crawl. They are not drawn to garages and houses nor are they searching for food, warmth, or mates.

Wandering millipedes eventually bump into the house where they find small gaps or cracks. They crawl into these small openings as a shelter from the dryness of the coming daytime. Millipedes hide during the day under the bottom edge of the garage door, in cracks along the house, sidewalk or driveway and in gaps in the foundation.

Openings in the foundation allow the millipedes to enter the house, where they continue wandering until they find a place to hide or until they die from lack of moisture, coiled in the corners of a room.

As much as possible, millipede control should be directed at keeping them outdoors. Cracks, gaps and other points of entry around windows and doors and in foundation walls should be sealed as much as possible. Reducing their numbers outside at the source by removing organic matter such as plant mulch and dead leaves from against the house may help.

Insecticides are of little benefit in controlling millipedes because of the protected areas where they originate and because of the long distances they migrate. Some sources of millipedes such as woodlands and crop reserve program fields can produce large numbers of millipedes that invade from distances of 50 feet or more. Spraying on and along the foundation usually has little effect, if any. The indoor use of household insecticides also provides little benefit.

Millipedes that wander indoors usually die in a short time because of the dryness in the house. Sweeping or vacuuming up the invaders and discarding them is the most practical option.

No matter what you call them, chances are you will find millipedes in your garage or home this fall.