Pill bugs and Sow Bugs of the Order Arthropoda (arthropod means segmented body and jointed appendages), Class Crustacea, Order Isopoda (isos meaning equal and podes meaning feet), and have a hard armored exoskeleton and jointed limbs. Both creatures are nocturnal, and each has seven pairs of legs at maturity. They are scavengers, feeding on both dead and live plant and animal debris.
Their many common names include pill bugs, sow bugs, potato bugs, rolypolys and woodlice. People often confuse pill bugs and sow bugs, but, to protect their soft undersides when disturbed or to keep their gills from drying out, pill bugs can roll into a ball with their legs tucked inside; sowbugs cannot do this.
Sow bugs have oval bodies when viewed from above. Their backs consist of a number of overlapping articulating plates. Their antennae reach about half the length of their bodies. Most are grayish, and grow to about 9/16 inch (15 mm) long and 5/16 inch (8 mm) wide. The pill bug, on the other hand, has a rounder back from side to side, and a deeper body from back to legs. Their color varies, but is usually grayish brown, and they reach less than 1 inch (2.5 cm) in length at maturity.
As members of the Class Crustacea, they are closely related to lobsters, crabs and shrimp. Most crustaceans live in or near water, and as dry-land crustaceans, pill bugs and sow bugs still require damp habitats due to the delicate gill-like breathing organs on their undersides, which must be kept moist to work. They prefer to live in humid sheltered areas that have plentiful decaying vegetation, such as under logs, stones, boards, leaves and leaf litter, under pots or bricks or even in damp basements.