Pill bugs, also called a "potato bug" or "doodle bug", is actually called a wood louse.  Although commonly thought of as insects, they are actually crustaceans, the same as a lobster, crab, or crayfish.  The body of the pill bug is composed of several segments.  Using special muscles the pill bug can roll itself into a ball, leaving only it's tough outer shell exposed.  This distinguishes from the sow bug, which appears similar to the pill bug but cannot roll itself into a ball.

    Pill bug can typically be found in dark, damp places such as the underside of rocks, fallen trees, and deep grasses.  They typically hide during the day, coming out only at night to feed.  Some desert-dwelling pill bugs will even burrow deep into the sand to avoid the daytime heat.