The cerci are generally long as well, especially in the aquatic nymphs. The wings are almost always present but are sometimes very short. They are folded horizontally back over the body. These characters help distinguish them from Dermaptera and Embioptera which they superfically resemble and to which they are probably closely related. The immatures are variously called larvae, or nymphs or naiads, but are most frequently referred to as nymphs.
All nymphs are aquatic, and resemble the adults in many respects.
They also have three-segmented tarsi. The nymphs always have long cerci and never a third central tail or median caudal filament. Gills, if they have them, can occur on various parts of the thorax and abdomen and are composed only of filaments, not plates. The nymphs of stoneflies dwell in aquatic habitats, although there are some species in the southern hemisphere which spend much time on damp land. In general the preferred habitat is rocky streams with a noticeable current, but there are species that live in sandy places.