Millipedes and most centipedes prefer to live outdoors in damp habitats. They can be found under logs, mulch, leaves and rocks. Millipedes feed on decaying plant matter and are important decomposers. Centipedes are predators and eat insects, and other small arthropods.
Millipedes are brown to black in color and usually 1 to 1 1/2 inch long. They have a smooth cylindrical body and will curl up when disturbed or dead. You can tell the difference between millipedes and centipedes by looking at the legs. Millipede legs are short and underneath the body, whereas centipede legs are long and stick out along the sides of their bodies. Millipedes have two pairs of legs per body segment, while centipedes have one pair per segment.
The house centipede, Scutigera coleoptrata, is a centipede species that is capable of living and reproducing in buildings. The body is brown to grayish yellow and has three dark stripes on top. The house centipede is about 1 1/2 inches long and has very long slender legs. The house centipede is active at night and feeds primarily on small insects such as cockroaches, and other arthropods. Centipedes are considered beneficial because they eat other insects; however, most people don't like seeing them running across the floor.
Millipedes can become a pest when they wander into buildings. However, unlike the house centipede millipedes do not reproduce indoors. Millipedes also migrate long distances during certain times of the year (varies with the weather, but commonly in spring or fall) and will occasionally enter structures in large numbers these migrations.
Management of centipedes and millipedes needs to focus on reducing the number entering the home by sealing cracks in foundations and around doors. Also, reducing centipede and millipede habitat around the foundation will help. They prefer moisture, so you can reduce suitable habitat by raking back mulch from the foundation, keeping plantings trimmed to allow sunlight to dry the soil, and letting soil dry between watering. Perimeter spraying of insecticides are of limited benefit in controlling centipedes and millipedes because the products do not always reach their protected habitats.
When centipedes and millipedes get indoors it is best to remove them with a vacuum or broom. Sticky traps can be placed against walls near entryways in areas where they are commonly observed. Reducing moisture and removing hiding places (old newspapers, boxes, etc) will also help in managing these occasional invaders. Indoor use of insecticides is not recommended for controlling millipedes because they usually die in a short time because of the dryness. Controlling house centipedes is best accomplished by reducing the number of insects they are using for food.
This article originally appeared in the 1/16/2004 issue.