PLECOPTERA OF NORTH AMERICA 177 



Subgenital plate of female produced over about 

 half the length of segment 9, and bearing in 

 the middle a short declivitous narrowed por- 

 tion trijuncta 



8. Head and thorax wholly blackish ; no extra cross- 



veins beyond the cord. Female subgenital plate 

 not produced, hind margin entire. Male genital 

 hooks short cylindrical ; hammer large, longi- 

 tudinally rectangular, surface ridged ; no spines 



above on segments 9 and 10 theodora 



Head and thorax pale or obscure, never wholly 

 blackish 9 



9. Usually with no crossveins beyond the cord; fe- 



male subgenital plate not produced; western 



species 10 



With crossveins beyond the cord ; female sub- 

 genital plate produced and variously modified- 11 



10. Vein Sc weak and indefinite at its tip. Female 



subgenital plate cut straight across apex. Male 

 genital hooks flat, triangular ; hammer large, 

 transversely oval ; segments 9 and 10 above 

 with short spines. Expanse of wings 50-70 



mm. depressa 



Vein Sc stronger and definite at its tips. Fe- 

 male subgenital plate not produced but some- 

 what emarginate in middle, 9th ventral seg- 

 ment of female with a rounded spot each side. 

 Male genital hooks cylindrical ; hammer longi- 

 tudinally rectangular; no spines above on seg- 

 ments 9 and 10. Expanse of wings 40-55 mm. 

 calif ornica 



11. Prothorax quadrangular 12 



Prothorax strongly narrowed behind georgiana 



12. Median longitudinal depressed area between the 



rugosities of the pronotum wide (about 1/6 of 

 width of pronotum). Male genital hooks flat, 

 short and very broadly triangular, as wide as 

 long ; hammer transversely oval ; female sub- 

 genital plate produced, and evenly rounded. 



Western species 13 



Median longitudinal area of pronotum narrow 

 (about 1/10 of width of pronotum) ; male geni- 

 tal hooks not as wide as long; female subgeni- 

 tal plate variously modified. Eastern species__ 14 



