STREAM BUGS AS BIOMONITORS
Guide to Pacific Northwest Macroinvertebrate Monitoring and Identification
Jeff Adams
with Mace Vaughan and Scott Hoffman Black - The Xerces Society (www.xerces.org)

The common name for Plecoptera is derived from the tendency of the stonefly larvae (also called nymphs) to be found in rocky substrates of streams, rivers, or lake margins. Stoneflies are a well know and well loved group to fly fishers and fish alike. They are important predators and shredders in aquatic ecosystems and, as a group, are especially sensitive to human disturbance in watersheds.

Plecoptera are one of the most ancient insect orders. They go through incomplete metamorphosis (skip the pupal stage) and as adults, look much like they did as nymphs. Some adults even still have gill remnants on their thorax or neck. Stonefly adults are generally weak fliers and are only found close to stream, river, or lake margins where the nymphs are likely to be found. The nymphs occur mostly in flowing water, but can be found under the stones of rocky lake margins or (in the case of one Capniidae species) deep in Lake Tahoe.

Plecoptera are typically flattened and well-adapted for living under and between rocky substrates. They always have two tails, and each tail has many small segments (some common mayflies also have two tails but most have three). They also have two claws at the end of each leg and have finger-like gills on the head, thorax, or between the tails, if they have gills at all. The never have flat, plate-like gills on the sides of their abdominal segments.

Family list:
Capniidae (snowflies or slender winter stoneflies)
Chloroperlidae (sallflies and little green stoneflies)
Leuctridae (needleflies or rolledwinged stoneflies)
Nemouridae (forestflies or little brown stoneflies)
Peltoperlidae (roachflies or roachlike stoneflies)
Perlidae (golden stoneflies, stones, or common stoneflies)
Perlodidae (stripetails and springflies, yellow stoneflies)
Pteronarcyidae (salmonflies or giant stoneflies)
Taeniopterygidae (willowflies)

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