Plecoptera

Plecoptera, commonly known as stoneflies, are an order of aquatic insects with about 3,500 to 4,000 described species. Adults are typically slender, with long antennae, two pairs of membranous wings held flat over the abdomen when at rest, and paired cerci. Nymphs, or naiads, are aquatic and usually elongate with soft bodies, gills along the thorax or abdomen, and strong legs. Wing venation varies among groups and can aid in identification.

They undergo incomplete metamorphosis. Eggs are laid in or near streams; naiads develop in water for several months to several years, depending on the species, before emerging as winged adults. Adults are generally short‑lived and do not feed extensively; mating occurs near water, and eggs are deposited back into streams. Emergence can be synchronized and sometimes conspicuous.

Habitat and ecology: Stoneflies require cold, clean, well‑oxygenated freshwater and are typically found in streams and rivers with stable substrates. Their sensitivity to pollution makes them useful bioindicators of water quality. They occur worldwide, though species richness is higher in temperate regions. Naiads are mostly predatory or detritivorous, while adults often feed little or not at all, and both stages contribute to aquatic food webs.

Role and fossil record: In ecosystems, stoneflies contribute as predators and as prey for fish and birds. Some nymphs are important forage for trout and other game fish. Stoneflies have a long fossil record dating to the late Paleozoic, with fossils known from the Carboniferous and Permian periods, and the group persists to the present.