[3] Plecoptera are found in both the Southern and Northern Hemispheres, and the populations are quite distinct, although the evolutionary evidence suggests species may have crossed the equator on a number of occasions before once again becoming geographically isolated.

They have simple mouthparts with chewing mandibles, long, multiple-segmented antennae, large compound eyes, and two or three ocelli.

[6] The name "Plecoptera" literally means "braided-wings", from the Ancient Greek plekein (πλέκειν, "to braid") and pteryx (πτέρυξ, "wing").

A few wingless species, such as the Lake Tahoe benthic stonefly ("Capnia" lacustra[Note 1]) or Baikaloperla, are the only known insects, perhaps with the exception of Halobates, that are exclusively aquatic from birth to death.

[11] Most species are herbivorous as nymphs, feeding on submerged leaves and benthic algae, but many are hunters of other aquatic arthropods.

[6] The insects remain in the nymphal form for one to four years, depending on species, and undergo from 12 to 36 molts before emerging and becoming terrestrial as adults.

Austroperlidae Grypoterygidae Diamphipnoidae Eustheniidae Leuctridae Taeniopterygidae Scopuridae Capniidae Nemouridae Notonemouridae Peltoperlidae Pteronarcyidae Styloperlidae Perlidae Chloroperlidae Perlodidae