Pill Bugs

Pill Bug Facts

• Scientific Name: Armadillidium vulgare, the species most often found around homes
• Nicknames: Roly-poly, for the way it curls into a ball. Other common names include wood louse and potato bug.
• Location: Damp, shaded ground in yards, gardens, woods and fields on most continents, and common throughout Florida
• Size: Adults are usually under 3/4 inch long, and most are closer to 1/2 inch

Pill Bug Appearance and Behavior

A pill bug’s back is made of overlapping hard plates that work like a suit of armor and let it curl up. The body has three main regions: a head, a midsection (thorax) of seven segments, and a short tail section (abdomen). Each thorax segment carries one pair of legs, so an adult walks on 14 legs. The head holds the eyes, the mouthparts and two pairs of antennae. Only one pair is easy to see. The other pair is tiny.

Pill Bug, Sow Bug or Millipede?

Pill bugs are not insects. They are land-dwelling crustaceans called isopods, in the same broad group as shrimp, crabs and crayfish. Adults are slate gray to dark gray, oval and strongly domed, and they can roll into a tight ball. Several similar creatures are easy to mix up:

• Sow bugs look similar but are flatter, cannot roll into a ball, and have two short, tail-like points sticking out from the rear.
• Millipedes are long and cylindrical, with two pairs of legs on most body segments. Some coil into a spiral when disturbed, but they don’t form a round ball.

Pill bugs live in damp, sheltered places such as leaf litter, mulch, compost, rotting logs and under stones. They feed mostly on decaying leaves and other dead plant matter and fungi, and sometimes on tender seedlings or soft fruit lying on the ground. Rolling up protects them from predators and helps slow water loss. Young pill bugs grow by molting in two halves, shedding the rear half of the old shell first and the front half a little later.

The pill bug most often found around homes, Armadillidium vulgare, originally came from the Mediterranean region and is now widespread across North America, including Florida, where it is a common sight in yards and gardens. It is active mostly at night. If they’re coming indoors, see our pill bug infestation page.