A wood louse is a small gray or brown creature with a segmented, armored body that lives in damp, dark places like under rocks, logs, or flowerpots. Despite its name, a wood louse isn't actually a louse (which is an insect). It's a crustacean, more closely related to crabs and lobsters than to bugs, though it lives on land rather than in water.

Wood lice have seven pairs of legs and two small antennae. When threatened, some species can roll up into a tight ball to protect themselves, which is why they're sometimes called pill bugs or roly-polies. Others, called sow bugs, can't roll up.

These harmless creatures play an important role in nature by eating dead leaves and rotting wood, helping break them down into soil. If you gently pick one up, you'll notice it moves slowly and feels slightly rough. Wood lice need moisture to survive, so they hide in damp spots during the day and come out at night when the air is cooler and wetter.

You might find wood lice in your garden, basement, or anywhere that stays moist and shaded. They're completely harmless to people and plants, though finding a lot of them indoors might mean you have a moisture problem somewhere in your home.