Q. We always have a few of these insects in our basement that the neighbor kid calls pillbugs. They don’t seem to really do anything but I’d like to know where they’re coming from. Any ideas?

A. I do have a few ideas. Pillbugs are outside arthropods that occasionally move indoors, usually driven by wet weather outside. Pillbugs are actually crustaceans, not insects. They’re more closely related to crabs than beetles, and they even look kind of prehistoric. When I was a kid, we used to love to play with them, making them roll into balls. That’s their defensive behavior when threatened. We called them rollie-pollies but they’re sometimes called woodlice (although they are not related to lice at all).

Outside, pillbugs are found in damp sites around foundations: under leaves, mulch, stones, splash blocks, flower pots, grass clippings, compost, or under bark. They are scavengers on moist, decaying plant materials like overripe fruit. They sometimes feed on small plants and rotting wood.

Indoors, pillbugs are found in damp areas, around door thresholds or sliding doors, in garages, crawlspaces, or basements. They enter through small gaps around doors or other openings, or they may be carried indoors in potted plants or firewood. An indoor invasion usually means you have a large population of pillbugs outside around the foundation.

The pillbug is often confused with the very similar sowbug. The key difference is that the sowbug cannot roll into a ball. Pillbugs are grayish and about 2/3-inch long, with seven pairs of legs. They are active at night when humidity is higher and temperatures are lower; they hide during the day. They don’t bite and they don’t do any damage indoors.

Since pillbugs don’t have the waxy cuticle of insects, they dry out quickly. They survive only a day or two in most indoor environments, so indoor control is rarely necessary. You can keep them from coming in though by sealing openings near the foundation and around doors, and with a perimeter insecticide treatment around the outside of your house. Our experienced pest control technicians at Colonial are prepared to do both.

You can also reduce the numbers of pillbugs (and many other foundation pests) by changing the conditions around your foundation that favor these kinds of pests. Remove sources of food and shelter such as leaves, mulch, grass clippings, and overripe fruit or vegetables on the ground. Firewood, boards, and stones should be stacked up off the ground and away from building foundations. Ventilating  crawlspaces or basements that are too moist will help, too.