Plecoptera: Stoneflies “pleco” = folded

Number of Stonefly Species (from North American Stonefly List by Bill Stark http://www.mc.edu/campus/users/stark/Sfly0102.htm)   Pennsylvania North America World Families 9 10 15 Species 132 465 >2000  

Plecoptera: Stoneflies Very sensitive indicators of clean, oxygenated waters Important food source for game fish Common Families Perlidae-common stoneflies Taeniopterygidae-winter stoneflies; emerge January to April Nemouridae-spring stoneflies; emerge April to June Most diverse in small, cool streams that do not exceed 25F and are nearly oxygen saturated Strong preference for coarse substrates Almost exclusively lotic Some are shredder-detritivores; others are predators on midges, blackflies and mayflies

Life History Most have one generation/yr, but some require two years Various species emerge in all months Egg masses deposited on surface of water; breaks apart; eggs stick to bottom; hatch in 3-4 weeks 10-11 months as larvae (range 6 months-3 years), molting 10-22 times May respond to predators by playing dead; rejected by sculpins; one family autohemorrages Prior to emergence they may enter drift community; leave water at night; molt in ~ 10 minutes Move to vegetation to pass teneral stage; Adults live 1-4 wks; mostly active at night Sexes ‘drum’ to each other to locate mates

Plecoptera: Stoneflies Hemimetabolous: egg  nymph (naiad)  adult Immatures Antennae long and filiform Body dorsoventrally flattened Ventral tracheal gills present around head, legs, or anus Thoracic segments covered by dorsal sclerite Two long, multisegmented cerci Two tarsal claws Adults Antennae long and filiform Two long, multisegmented cerci 2 prs of membranous wings with many veins Hind wings much wider than fore wings; thus hind wings are pleated to fit under the fore wings

Nymph

Adults

The interesting case of Winter Stoneflies Two families live this ‘backward’ life history Eggs hatch in late winter When water warms they migrate 1 m or more to the rocky hyporheic zone; enter diapause for 3-6 months Cool water stimulates feeding & growth Emerge in winter; Dark colored; often on rocks; why?

Ecological Role As shredders, they break downleaves, twigs, etc. Create greater surface area for colonization by bacteria, fungi, etc., as well as for other invertebrates Important food for other organisms Probably the most pollution sensitive order of aquatic insects

http://www. cals. ncsu. edu/course/ent425/compendium/stonef~1 http://www.cals.ncsu.edu/course/ent425/compendium/stonef~1.html#class

Stoneflies of Pennsylvania

Nymphs

Adults

Links Plecoptera: http://www.cals.ncsu.edu/course/ent425/compendium/stonef~1.html#class