Plecoptera

From Wikipedia, the free encyclopedia

iPlecoptera

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Infraclass:	Neoptera
Order:	Plecoptera Burmeister, 1839

Suborders

Plecoptera are an order of insects, commonly known as stoneflies. There are some 1,700 recorded species worldwide.

The nymphs are aquatic and live in the benthic littoral zone of lakes and streams. Nymphs of this order are primarily hunters of other aquatic arthropods or shredder/gatherers. They undergo many molts as aquatic nymphs (10 instars?) before emerging and becoming terrestrial as adults.

The name comes from the Greek pleikein ("braided") and ptera ("wing"). They possess two pairs of wings which are membranous and fold flat over the back. Both nymphs and adults have long paired cerci, or tails, projecting from the tip of their abdomens.

Image:Plecoptera-perlidae1-sp.gif

A few wingless species such as Capnia lacustra are the only known insects that are fully aquatic from birth to death <ref>Holst, E. M. Lake Tahoe benthic stonefly (Capnia lacustra) (PDF) in: (2000) Murhy, D. D. & C. M. Knopp: Lake Tahoe Watershed Assessment. USDA, O-118–O-120.</ref>.

They are believed to be one of the most primitive groups of insects with close relatives identified from the Carboniferous and Lower Permian geological periods.

Plectoptera are found in both the Southern and Northern hemispheres, and the populations are quite distinct although the evolutionary evidence suggests that species may have crossed the equator on a number of occasions before once again becoming geographically isolated <ref>Hynes, H. B. N. (1993). Adults and Nymphs of British Stoneflies. Freshwater Biological Association. ISBN 0-900386-28-2.</ref>.

All species of Plecoptera are pollution intolerant and their presence in a stream or still water is usually an indicator of good or excellent water quality.