Department of Entomology

Plecoptera (Stoneflies, Salmonflies)

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Plecoptera - Brigham Young/VPI & SU PCD0330019

I. Background Information

A. Origin of name

1. pleco, folded or pleated; ptera, wings
2. hind wing must be folded to fit under forewing

B. Classification

1. Number of families and species in North America north of Mexico - 9 families, 578 species

C. Common names - stoneflies; also salmonflies

D. Type of metamorphosis - simple (hemimetabolous)

E. Phylogenetic relationships - neopterous exopterygota (closely related to Orthopteroid group)

II. Biological Summary for Order

A. Life history

1. Eggs - in masses of up to 1000; always in water; masses fall apart; usually hatch in 3 to 4 weeks
2. Immature stages - nymphs; usually 10 to 11 months (some 2 to 3 years); usually 10 or 11 instars (ranges from 6 to 22)
3. Adults
a) most live 7 to 28 days
b) crawl out of H₂O to emerge
4. Number of generations per year - most univoltine (some semivoltine or merovoltine)
5. Time of emergence - most spring and summer; some only in fall or winter (adult stoneflies can be collected at any time of the year)
6. Delays in development - winter stoneflies diapause for 3 to 6 months as eggs in warm months

B. Habitat and habits

1. Adults - do not disperse very far from aquatic habitat; don't fly that much; very inconspicuous, hiding in vegetation, debris, rocks
2. Nymphs - only found in well-oxygenated (very sensitive to pollution) flowing waters; crawl about in rocks, debris

C. Food

1. Adults - soft vegetation such as flowers, fruits, pollen, lichens, algae
2. Nymphs - either other invertebrates or plant detritus

D. Respiration of immature stages

1. Closed tracheal system; with or without gills (filamentous gills mostly on thorax, if present)
2. Probably also body respiration

E. Behavior

1. Adults - males and females use species-specific drumming to locate each other

F. Significance

No adverse economic significance; ecological significance in detritus dynamics and regulating community structure

Collecting and Preserving Adults

Best collected by sweep netting in vegetation near water and visually inspecting likely hiding places; specialists collect mature nymphs and rear to adults; some species are attracted to lights; preserve in 70% ethanol