THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

Psephenidae inhabit running waters and are not likely to be found in wetlands. It's hard to mistake a water penny larva for any other macroinvertebrate. Psephenid larvae are oval and disc-shaped, with armored segments that hide the head and legs when viewed from above. Their unique body design is well suited to living on rocks in strong currents, where they cling to the surface of rocks like little suction cups, grazing on tiny algae.

Adult water pennies live in riparian areas and in moist areas under streamside rocks and logs. Adults can be separated from other beetle families because they do not swim, and have relatively soft oval-shaped bodies. Antennae are variable among genera; some are highly modified into long brushes and others are fairly thick in size.