Stonefly

Stoneflies are insects of the order Plecoptera. They are characterized by slender bodies and two long cerci (tails) at the end of the abdomen. The immature stages, or naiads, are aquatic and breathe with gills on the thorax or abdomen; adults have two pairs of membranous wings that are typically held flat over the abdomen when at rest. In many species, adult mouthparts are reduced and they feed little or not at all.

Stoneflies occur worldwide, with greatest diversity in cool temperate regions. They inhabit streams and rivers that are clean and well oxygenated. Nymphs live under stones, in riffle zones, or among leaf litter. Because of their sensitivity to pollution and sediment, stoneflies are frequently used as indicators of freshwater quality.

Life cycle is hemimetabolous: eggs are laid in or near water, hatching into aquatic naiads that molt through several instars before emerging as winged adults. Naiads may live for several months to years, depending on species; adults typically live only a short time, often days to weeks, mainly for reproduction. Nymphs are an important food source for fish and other aquatic predators; adults contribute to terrestrial food webs as prey for birds and other animals.

Stoneflies are considered an ancient and ecologically important group within freshwater ecosystems. They are commonly studied in freshwater biology, aquatic ecology, and biomonitoring due to their ecological sensitivity and role in stream food webs.