Plecoptera epitomizes cold, clear, fresh water; they are excellent indicators of good water quality. They develop as nymphs in the water and live rather reclusively very near to water. An interesting tidbit is the first recorded fly tied by a human mimicked a stonefly! These insects are close relatives of cockroaches but they have tails and the ability to fold their wings over their backs.
Their common name is thought to come from their larvae habit of crawling around and on top of stones and rocks. Their taxonomic name is derived from the “pleated wings” they have.
Here’s an interesting blog post, The Dragonfly Woman, written by an aquatic entomologist. In this particular link, she’s discussing how the know if the larvae you find is a stonefly, a mayfly, or a damselfly. If you’re a fly-fisherperson or just like to check out the local aquatic insect life, this is a good read.
Northern Prairie Wildlife Research Center has some good info on stoneflies with a map of reported locations. One can look at their state to see what species have been noted to be there.
Perlidae (Common Stoneflies)
There are 400 species and most of them live in the northern hemisphere.
Perlesta sp – Common Stonefly
Perlesta nitida – Tiny Stonefly
Pteronarcyidae (Giant Stoneflies)
This is a primitive family of stoneflies that can be found all over the US. They are the largest stoneflies. The eggs are rounded, highly sculptured, and have a large cap. Because each species’ eggs are distinctly shaped, one can ID them from these.
Pteronarcys sp – Giant Stonefly
These are the largest stoneflies in the northeast; this one was 2-2 ¼” long. Hemimetabolous, these large “summer” stoneflies spend 2-3 years in water as nymphs before they emerge as adults and come out of the water.