What is a distinctive feature of stoneflies?

Stoneflies are characterized by having two tails, known as cerci, that extend from the rear of their bodies. This feature is significant as it distinguishes them from many other aquatic insects. The presence of two tails is typical of the order Plecoptera, to which stoneflies belong.

In addition, stoneflies possess a pair of membranous wings, with many species exhibiting some form of wing structure, but they do not have three pairs of wings, making three pairs of wings an incorrect description. Gills are present in stoneflies, but rather than being located on the legs, these aquatic insects typically have them associated with their abdominal segments. Thus, the defining characteristic of having two tails is what makes this feature distinctive in identifying stoneflies.