175 

 Jewett: Plecoptera 



10. 



11. 



12. 



13. 



14, 



6:39., Ventral view of female terminalia of I sogenus. 

 a, yakimae; b, tostonus (Ricker, 1952). 



Needham and Claassen 1925) misnomus (Claassen) 1936 

 A median mesosternal ridge present running from the 

 fork of the Y to the transverse ridge; submental gills 

 long; (fig. 6:36a, d); Cordillera east to Manitoba .... 



(subgenus Iso- 



genoides Klapalek 1912) frontalis colubrinus Hagen 1874 

 Median mesosternal ridge absent from the fork of the 



Y to the transverse ridge 5 



No lobe on the 7th male sternite; submental gills at 

 least twice as long as wide; Mississippi Valley .... 



(subgenus Hydroperla Frison 1935) 



A well-developed lobe on the male 7th sternite; sub- 

 mental gills mere stubs or absent 6 



Lateral stylets absent from the male supra-anal apparatus 



7 



Lateral stylets present 12 



Produced tip of the anterior sclerotized band of the 

 supra-anal process normally coiled within the process 



(subgenus Kogotus Ricker 1952) 8 



Tip of the supra-anal process not coiled 9 



A large, three-rayed spot on the head, the middle ray 

 within the ocellar triangle, the others reaching the eye; 

 paragenital plates of male subacute (figs. 6:38/; ?, 



6:38a) nonus (Needham and Claassen) 1925 



Head mostly brown without a yellow rayed spot; tips 

 of paragenital plates of male rounded, upturned and 



spinulose (fig. 6:366) 



alameda (Needham and Claassen) 1925 



The basal support of the supra-anal apparatus situated 

 at the anterior edge of the 10th tergite; eastern North 



America (subgenus Helopicus Ricker 1952) 



Basal support of the supra-anal process situated at 

 least halfway back on the 10th segment, much behind 



the anterior margin 10 



Supra-anal process terminating in an eversible lash 

 scarcely surrounded by a cowl posteriorly; New York to 



Carolinas and Georgia (subgenus Remenus 



Ricker 1952) bilobatns (Needham and Claassen) 1925 

 Supra-anal process of normal length and with a complete 



cowl behind 11 



Short submental gills present; Colorado, Wyoming, 



Montana 



(subgenus Pictetia Banks 1947) expansus (Banks) 1920 

 Submental gills completely lacking; southern Appa- 

 lachians (subgenus Yugus Ricker 1952) 



Lateral stylets greatly exceeding the tiny tip of the 

 supra-anal process which is often difficult to find; 



eastern North America (subgenus Uiploperla 



Needham and Claassen 1925) duplicatus (Banks) 1920 

 Lateral stylets no longer than the well-developed tip 



of the supra-anal process 13 



Submental gills completely absent; lateral stylets 



slender, acute (subgenus Cultus Ricker 1952) 14 



Submental gills short but distinct; lateral stylets not 



as above 15 



Hind head yellow centrally and with yellow lobes ex- 

 tending forward between the ocelli and between eyes 



rig. 6:40. Oiura know/torn, terminalia. o, dorsal view of male; b, 

 ventral view of female (a, Frison, 1937; b, Frison, 1942b). 



and ocelli, 3 in all (fig. 6:386, c); British Columbia to 

 Oregon pilatus (Frison) 1942 



— Head mostly yellow, the only important dark marking 

 being the bands which join the anterior of the lateral 

 ocelli (figs. 6:38^; 6:396); British Columbia to Cali- 

 fornia, Montana, and Wyoming .... tostonus Ricker 1952 



15. Submental gills conical; lateral stylets hooked at the 

 tip; eastern North America (sub- 

 genus Malirekus Ricker 1952) hastatus f Banks) 1920 



— Submental gills rounded; lateral stylets rounded at the 

 tip (see also couplet 3) 



(subgenus Chernokrilus (in part) 



Subfamily PERLOCINAE 



This subfamily is represented in North America by 

 the genus Diura Billberg 1820, which comprises two 

 subgenera, Diura, s. s., confined to the Appalachian 

 region, and the monotypic Dolkrila Ricker 1952 which 

 is cordilleran. The latter has not been recorded from 

 California, but D. (Dolkrila) knowltoni (Frison) 1937 

 (fig. 6:40a, b) occurs to the north in Oregon. 



Subfamily ISOPERLINAE 



This group contains the genera Calliperla Banks 

 1948, Isoperla Banks 1906, and Rickera Jewett 1954. 

 Calliperla has but one species, luctuosa (Banks) 

 1906 (fig. 6:41a,Z») which occurs in California and 

 Oregon. Several species of Isoperla occur in the 

 Palaearctic region, but the greatest development of 

 the genus occurs in North America from which about 

 forty species have been described. The genus con- 

 tains several complexes but has not been broken 

 into subgenera. The following key and accompanying 

 illustrations may be used to classify the described 

 California species. Much work needs to be done on 

 this genus, particularly on our western species. 

 Nymphs of only a few California species are known. 



Key to Adults of California Species of Isoperla 



1. Tip of male 10th tergite with 2 small recurved proc- 

 esses; no lobe on male 8th sternite (fig. 6:42a); female 

 8th sternite not produced except for a small median 

 process (fig. 6:426); head with a complete median dark 

 stripe, darkest between the ocelli; pronotum with broad 

 median and lateral light stripes; Washington to Cali- 

 fornia trictura (Hoppe) 1938 



'Adapted in part (rom Ricker (1943). 



