THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

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

Perlidae are large, powerful stoneflies that serve an important predatory role in streams. They eat a wide variety of insects, including midges, mayflies, and net spinning caddisflies, and sometimes feed on fish eggs and very young fish.

Perlidae are often seen doing "push-ups" in a sample tray to keep fresh, oxygenated water moving around their gills. They perform similar aerobic activities in nature as territorial behavior to warn off competitors. They are generally very active and can be observed running around the collection tray. Occasionally they will eat everything that comes in contact with their antennae, so watch that they don't bias your sample!

Perlidae have fluffy gill tufts around the base of each leg or between their tails, but never on the underside of their abdomens. This characteristic separates this group from all other stream invertebrates. It can be easy to mistake early instar Perlidae for Perlodidae, because their gill clusters may be reduced to only a few filaments or even nubs, but Perlodidae usually have large heads compared to their bodies.