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Order Plecoptera - Stoneflies

Perlidae: Perlinella ephyre - Perlinella ephyre Chloroperlidae: Sweltsa onkos - Sweltsa onkos Isogenoides hansoni Stonefly? - Pteronarcys - female porch light visitor - Neoperla Stonefly - Zapada oregonensis Wynoochee Chloroperlid - Kathroperla Stonefly Larva
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Plecoptera (Stoneflies)
Other Common Names
on guide pages, the common names used in(1) are provided in the title; those used in(2)(3) are listed as "Other Common Names"
Explanation of Names
Greek plektos 'twisted' + pteron 'wing'; refers to the folded posterior region of the resting hind wing
Numbers
worldwide, ~3,400 spp. in ~300 genera of 18 families(4); >670 spp. in >100 genera of 9 families in our area(5) [600 spp. in the US(2)]; of the two suborders one (~330 spp. in 6 families) is restricted to the southern hemisphere.
Species lists:(2)(5)(4)(6)(7)
Genera not yet in the Guide are listed in(8)
Overview of our fauna (* –taxa not yet in the guide; classification adapted from(5)(4)):
Order Plecoptera
SUPERFAMILY NEMOUROIDEA
Family Capniidae
Family Leuctridae
Family Nemouridae
SUPERFAMILY PERLOIDEA
Subfamily Chloroperlinae
Family Perlidae
Subfamily Acroneuriinae
Subfamily Perlinae
Family Perlodidae
Subfamily Perlodinae
SUPERFAMILY PTERONARCYOIDEA
Subfamily Pteronarcyinae
Size
4-60 mm
Identification
Adult: drab colored with four membranous wings held flat over the abdomen when at rest; front wings narrower than hind wings; expanded anal lobe of hind wing often folded fan-like at rest; wings of males of several species reduced or absent; antennae, long, slender, many-segmented; abdominal cerci often long and prominent; mouthparts adapted for chewing
Nymph: body flattened and elongate with two, usually long cerci; most nymphs have tufts of branched respiratory gills on sides of thorax and around bases of legs; the gills are filamentous, not plate-like or leaf-like
pictorial key to families with good wing venation diagrams
Helpful online pictoral keys in(9)
Range
mostly the cooler, temperate parts of the world
ranges/maps for NA species:(2)(5)
ranges/maps for all known taxa:(4)
Habitat
nymphs occur primarily under stones in cool unpolluted streams; some species occur along rocky shores of cold lakes, in cracks of submerged logs, and debris that accumulates around stones, branches, and water diversion grills
spring and summer adults may be found resting on stones and logs in the water, or on leaves and trunks of trees and shrubs near water; winter stoneflies are often attracted to concrete bridges over streams, and some species are commonly found on snow or resting on fence posts during the warmer days of late winter(10)
Season
adults of most species emerge during late spring and summer; however, the so-called "winter" stoneflies emerge and reproduce during the fall and coldest parts of the winter
Food
nymphs feed on algae, diatoms, mosses, and immature aquatic invertebrates, including mayflies and midges; most spring and summer adults do not feed, and are nocturnal; winter stoneflies are day-flying, and feed on blue-green algae and foliage
Life Cycle
females deposit several egg masses, which together may total more than 1,000 eggs, by flying over water or occasionally by crawling up to the water; some nymphs are known to molt 12-36 times, and require one to three years to mature; full-grown nymphs leave the water, cling to shoreline vegetation and debris, and molt into the adult stage
Remarks
nymphs of most spp. develop in cool, well-oxygenated water and do not tolerate pollution; therefore, their presence is an indicator of good water quality, and their absence in areas where they previously occurred may indicate pollution
See Also
mayfly (Ephemeroptera) nymphs are similar but all except a few genera have three caudal filaments and leaf-like gills on the abdomen
Internet References
Tree of Life chapter, by C.R. Nelson