The adults emerge and mate during the late winter and early spring, often while snow still covers the stream banks. The cerci may be long or short.
Stoneflies have two pairs of wings.
The aquatic nymphs are generally very similar to mayfly nymphs except that they have only two cerci at the tip of the abdomen. Stonefly nymphs have their gills on the thorax and about the base of the legs, while the mayfly nymphs have leaflike gills along the sides of the abdomen. The stoneflies have chewing mouthparts. Many adults, however, do not feed and have reduced or vestigial mouthparts. Some species are not even attracted to light.