/y\ 



V 



Fig. 6:12. o,c, diagram of mesosternal ridge pattern; b, sternal 

 plates of Peltoperla brev/s; a, Arcynopteryx (in part); c, Isogenus 

 (in part). (o,c, Ricker, 1952; b, Ricker, 1943). 



161 

 Jewett: Plecoptera 



— Body with few <>r n<. brli ties, none on the obea 



11 



11. Abdominal segments with a f<-w sli-nd 



ern North America Euoapnop Oka oto 1922 



— Abdominal segments with n<> bristles 12 



12. Inner margin of the hind wing pad with a notch about 

 half way from base to tip; Ntmooopnia has been re- 

 corded only from .North Carolina, Virginia, Arkansas, 

 Indiana, and Illinois where Capnia does not occur 



.... Capnia Pictet 1841 and Nemocapnia Banks 1938 



— Inner margin of the hind wing pad notched very close 

 to the tip if at all; east of Rooky Mountains 



Allocapnia Claassen 1928 



13. Coxae without gills Brachyptera Newport 1848 



— A single gill on each coxa ... .Taeniopteryx Pictet 1841 



14. Ventral abdominal gills on segment 3; western North 

 America Pteronarcella Banks 1900 



— No ventral abdominal gills on segment 3 



Pteronarcys Newman 1838 



15. Profusely branched gills at the lower angles of the 

 thorax PERLIDAE 24 



— Branched gills absent from the thorax 16 



16. Body usually pigmented in a distinct pattern; cerci 

 usually at least as long as the abdomen; pads of the 

 hind wing in nearly mature nymphs set at an angle so 

 that their central axis diverges considerably from the 

 axis of the body; gills absent or simple gills present 

 on submentum, thorax, or abdomen . . . PERLODIDAE 17 



— Body almost concolorous, without a pattern; cerci not 



Fig. 6:13. Nymph of Paraperla frontalis (Claassen, 1931). 



Fig. 6:14. Nymph of Alloperla borealis (Claassen, 1931). 



