What it looks like: 1-2 mm in length. This beetle has an elongated, oval-shaped body that is tapered at both ends. It is brown with short elytra that leave part of the abdomen exposed.

Where you'll find it: This species ranges from Mexico all the way up through Idaho.

Natural History: These beetles are aquatic, living in streams ranging from icy cold mountain creeks to hot springs. They feed on algae both as larvae and adults, and the adults carry an air supply under their elytra, as bubbles that cling to small hairs on the abdomen. The females produce only one large egg at a time, an unusual feature among beetles.