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. This is an interesting arrangement because the nemourids are uniquely northern hemisphere in distribution and the notonemourids are uniquely southern hemisphere in distribution. The Pteronarcyoidea are herbivorous throughout their aquatic lives.