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Stonefly (Plecoptera)

General Information about Stoneflies (Plecoptera)
Life history Stoneflies usually spend 10 months to 2 years living and growing as larvae in the water. When ready the larvae emerge from the water and transform into terrestrial adults.
Diversity There are 9 different families of stoneflies in North America.
Distinguishing
characteristics
 Most kinds of stoneflies have 2 long cerci (tails) and 2 tarsal claws (nails) at the end of each leg.
Habitat & Feeding Stoneflies can be found in most running waters and are commonly found in boulder, cobble, water-soaked wood, and leaf packs. Most species are predators or shredders (eat decaying plant material).
Water quality indicator status Stoneflies are usually associated with clean, cool flowing streams. Most stonefly taxa are sensitive to water pollution. Generally the presence of stoneflies is a reliable indicator of excellent water quality, but because of their specific habitat requirements, their absence does not necessarily mean the waterbody is polluted. Stonefly larvae are part of the widely used EPT Index (Ephemeroptera-Plectoptera-Trichoptera) to measure water quality condition. It is the number of different taxa of mayflies, stoneflies, and caddisflies.
Fun facts
  • In low oxygen conditions, larvae will do "push-ups" to move water across their gills.
  • One species, when the aquatic larva is pursued by a predator, will reflex bleed. They squeeze out drops of their blood; scientists think that this produces a bad smell or taste or is done to confuse the attacker.
Image of stonefly in the Perlidae family.
Perlidae family.
Image of stonefly in the Chloroperlidae family.
Chloroperlidae family.
Image of stonefly in the Pteronarcys genus.
Pteronarcys sp.
Image of stonefly in the Peltoperlidae family.
Peltoperlidae family