1. Plecoptera: Stoneflies “pleco” = folded

2. Number of Stonefly Species (from North American Stonefly List by Bill Stark
Pennsylvania
North America
World
Families 9 10 15
Species
132
465
>2000

3. 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

4. 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 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

5. 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

6. Nymph

7. Adults

8. 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?

9. 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

10. http://www. cals. ncsu. edu/course/ent425/compendium/stonef~1

11. Stoneflies of Pennsylvania

12. Nymphs

13. Adults

14. Links
Plecoptera: