Most of us have seen isopods (also known as sow bugs, pill bugs, potato bugs, roly-polies, doodlebugs) in compost bins or under logs or rocks. They usually have a hard gray exoskeleton covering a rounded body that they can roll into a ball when they feel threatened. Most genera of isopods live in the ocean where the are very diverse and can grow to be quite large. However, there are isopod genera that live in freshwater habitats, and some are common in wetlands.

Most of the isopods that are collected in the Northwest belong to the genus Caecidotea within the family Asellidae; isopods in this family were commonly found in a study of riverine wetlands in the Willamette Valley of Oregon. Another common genus, Asellus, was recently merged with the Caecidotea. Small, eyeless specimens of the hyporheic genera Calasellus and Salmasellus, also in the family Asellidae, may be collected periodically.

Isopods can be fairly easily separated from other invertebrates because they are flattened from top to bottom, are not terribly large, have many legs, and don't have a well developed muscular tail.

Key to Genera