In the spring, you may be seeing brownish black worms that curl up in a circle. You’ll find them indoors in small quantities or, in rare cases, overwhelming numbers. These small worms are most likely millipedes, characterized by their common defense action: curling into a circle. The smallest brownish black “worms” may be the result of a very recent hatching. If they survive, they’ll grow, molt and continue to make an appearance. However, without the right environment and food, most millipedes will quickly die inside your home.
The abundance of sightings in the spring means the females have laid their eggs outdoors. They’re prolific and can produce as many as 300 eggs at one time. Small batches of eggs are distributed in the ground litter, with youngsters emerging about three weeks later. In some regions, fall is another opportunity for millipedes to congregate abundantly in homes.
Millipedes also find lighted areas attractive. Homeowners report that lights around swimming pools and other nighttime attractions will draw these arthropods into the area. Remember, these small, brownish black “worms” are not insects at all; but do feed on many insect pests.
Are these brownish black worms harmful?
In general, millipedes are harmless, unlike their centipede counterparts, many of which can bite and sting. All millipedes, when disturbed, can emit a foul liquid that has the potential to irritate sensitive skin. The chemical emission can also become more serious if it reaches a human mouth or eyes. Larger, tropical millipedes, which are sometimes acquired as pets, may produce heavier concentrations of chemical defense. Hand washing is recommended after handling any millipede although the staining liquid may take a few days to disappear entirely. Otherwise, they won’t invade pantries or cause damage to home structures. They also do not carry diseases or munch on clothing.
Millipede sizes can range from about one-quarter of an inch up to one inch in length. Larger tropical millipedes can grow up to 12 inches long. They move rather slowly on short legs. Almost every body segment features two pairs of legs (as opposed to centipedes, which have only one pair per segment). No matter how large the millipede, though, they typically have far fewer legs than their nickname “thousand-leggers” suggests.
In the great outdoors, millipedes are beneficial creatures. They thrive in damp leaf litter and other debris, breaking it down while consuming pesky insects at the same time. When you see a home invasion, it’s usually because there is a population explosion outside. Millipedes are usually brownish black or a deep red-brown in color while centipedes can present many interesting shades. Millipedes thrive exclusively in the outdoors while some “house” centipedes can survive in or out.
Treating and spraying for millipede invasions is relatively useless. Cleaning up wet debris around the home can eliminate overpopulation. Caulking cracks and blocking drafty areas around doorways and windows will also help. Since millipedes feed on household pests, you can apply insecticides to eliminate those species, which will reduce the attractions of millipedes to your space.