Pill Bugs

General Information

The pill bug, Armadillidium vulgare, earns its name from its tendency to curl up into a ball when agitated. The ability also serves as the source for the pill bug’s many nicknames like roly poly, roll up bug, and roller. Although referred to as a bug, the pill bug is actually a crustacean. One of the only crustaceans capable of living on land, the pill bug is more closely related to crawfish and shrimp than any land-dwelling insects. Commonly found in cool, moist environments, pill bugs are distributed throughout .

Appearance & Identification

What do pill bugs look like?
When uncurled, pill bugs measure about half an inch in length. Oblong in shape, the pill bug has a convex top and a flat underside. The body consists of a head, thorax, and abdomen, all of which are covered by hard shell-like plates. Seven segmented plates overlap to protect the body, and the segmented order gives the pill bug the ability to curl up into a tight ball. Most pill bugs appear dark gray, but can also be brown or red in coloration. Seven pairs of pereopods, or short walking legs, connect at separate segments of the thorax. Like most crustaceans, the pill bug features two pairs of antennae that protrude from the head. The first pair of antennae is long and noticeable, while the second pair is small and inconspicuous.


Pill bugs are distributed worldwide, but are more commonly found in temperate regions. Pill bugs breathe through gills located on their underside and require moderate to high humidity for survival. \] The crustaceans prefer dark habitats and are usually found underneath natural debris such as rocks, logs, and piles of leaves. Pill bugs are mainly active at night to reduce risk of sun exposure, which could kill them by desiccation (drying them out). Pill bugs overwinter during colder months and reemerge when the environment warms up. Sometimes confused for the sowbug, a close relative of the same order, the pill bug can be distinguished by its ability to roll into a ball. The sowbug, by contrast, cannot form a ball.


What do pill bugs eat?
Pill bugs feed on detritus (decaying organic material). The crustaceans prefer rotting fruits and vegetables and decaying plant materials but may also feed on the decomposing remains of other arthropods. On occasion, pill bugs may eat plant roots and seedlings, usually in the absence of more desirable food. An estimated 10-percent of the pill bug’s diet comes from self-coprophagy, eating its own waste to pick up nutrients that were not processed during initial digestion.


Pill bugs usually reproduce in the warm months of late spring and early summer. A pregnant female carries eggs in a water-filled pouch called a marsupium. Once eggs hatch, offspring may remain in the pouch until they are developed enough to leave and forage for food. From eggs to developing young larvae, a female may carry a brood for a little over two months. A pill bug usually produces about two dozen young per brood. Environment (temperature and humidity) affects reproduction rate and pill bug populations. After leaving the marsupium, larvae molt within 24 hours and experience two more molts in the next three weeks. Developing pill bugs then molt once every two weeks for the next 20 weeks. Afterward, the crustaceans reach adulthood and molt at irregular intervals. Adult pill bugs live for about two years.

Problems Caused by Pill Bugs

Pill bugs do not pass diseases to humans and cannot damage homes or property. The presence of pill bugs in the home can be unsightly, especially if seen in large numbers and also indicate a potential moisture issue. Large populations outdoors may cause some damage to farms and gardens. Pill bugs typically feed on rotting materials but may threaten young plants and seedlings, as well.

Signs of Infestation

On occasion, pill bugs may accidently invade homes. The crustaceans can usually be found in areas of high moisture like crawlspaces and basements. Pill bugs in the home usually die from insufficient moisture, and dead bodies on the floor and in corners can alert homeowners to a possible infestation. Spotting living pill bugs on walls and floors affirms their presence. If pill bugs are found in the home, they can usually be found in large numbers in the soil around the foundation. Pulling up rocks or leaf litter will reveal if pill bugs are present outdoors.


Prevention begins with exclusion. Cracks and openings leading into the home should be sealed to prevent entry, with particular attention paid to foundation walls and ground-level areas. Next, homeowners want to remove outdoor plant debris that provides harborage to the isopods. Wood piles, grass clippings, and leaf litter should never rest against the home or be located near entry points. Homeowners want to water their lawns in the morning so that water dries by the afternoon. Inside the home, residents want to address any moisture problems, which can attract pill bugs. Focusing on the basement and first level, homeowners should run dehumidifiers in humid areas and repair any leaking pipes or water seepage points. Removing clutter from any damp areas also eliminates indoor harborage for the crustaceans.