162 



Jewett: Plecoptera 



has not been described and might not kev out here. 

 PARAPERLINAE 22 



— Eyes large and normally situated; body less elongate 

 (fig. 6: 14) CHLOROPERLINAE 23 



22. Head longer than wide Kathroperla Banks 1920 



— Head about as long as wide Paraperla Banks 1906 



23. Length of mature nymphs, excluding cerci, 5-7 mm., 

 the inner margins of the hind wing pads almost straight 

 . .Chloroperla Newman 1836 and Hastaperla Ricker 1935 



— Length of mature nymphs usually more than 6 mm.; the 

 inner margins of the hind wing pads curved or notched 



Alloperla Banks 1906 



24. Eyes situated much anterior to the hind margin of the 

 head (fig. 6:15) 25 



— Eyes situated close to the hind margin of the head 

 (fig. 6:16) 26 



25. Two ocelli; body uniformly colored; east of Rocky 



Fig. 6:15. Nymph of Perlinella drymo. (Claassen, 1931). 



more than 3/4 as long as the abdomen; pads of hind 

 wing nearly parallel to the axis of the body except in 

 mature Kathroperla which has the head elongated behind 



the eyes; external gills entirely lacking 



CHLOROPERLIDAE 21 



17. Gills absent from the thorax 18 



— Gills present on the thorax 



Arcynopteryx Klapalek 1904 (in part) 



18. Submental gills at least twice as long as their greatest 

 vddth 19 



— Submental gills about as wide as long, or absent ... 20 



19. Arms of the Y-ridge of the mesosternum meet or ap- 

 proach the anterior corners of the furcal pits (fig. 6:12a) 



Arcynopteryx (in part) 



— Arms of the Y-ridges meet the posterior corners of the 

 furcal pits (fig. 6: 12c) 



Isogenus Newman 1833 (in part) 



20. Abdominal segments usually with a longitudinal striped 

 pattern. (The nymph of Calliperla is unknown.) .... 



ISOPERLINAE Isoperla Banks 1906 



— Abdominal segments without a longitudinal striped 

 pattern Isogenus (in part) and Diura Billberg 1820 



21. Eyes small and set far forward; body narrow and elon- 

 gated (fig. 6:13). (The nymph of Utaperla Ricker 1952 



Fig. 6:16. Nymph of Per/esfo placida (Claassen, 1931). 



