PLECOPTERA OE NORTH AMER^A 75 



4. First anal vein, beyond the anal cell, straight; 



costal apical crossvein very strongly aslant ; tip 

 of vein Sc equidistant from veins C and R ; vein 



Rs 5-branched innubila 



First anal vein, beyond the anal cell, bent for- 

 ward to meet the cubito-anal crossvein at an 

 angle; tip of vein Sc usually much nearer vein 

 C than vein R 5 



5. Costal crossveins in the apical series not less 



numerous than in the proximal series alameda 



Costal crossveins in the apical series fewer than 

 in the proximal series 6 



6. Tip of subcostal vein in the fore wing almost 



joins the costa; male with apical dorsal lobes 

 of segment 10 developed as recurved genital 

 hooks, and with tip of supra-anal process 

 strongly decurved: the largest species (male, 



expanse 44 mm.) crosbyi 



Tip of subcostal vein less closely approximated to 

 the costa; male with lobes of segment 10 not 

 recurved mostly, convergent to rearward, and 

 with tip of the supra-anal process not strongly 

 decurved 7 



7. Wing membrane subhyaline with brown veins 8 



Wing membrane brown 16 



8. Blackish species with apex of abdomen yellow- 



ish 9 



Brownish or pale species with concolorous abdo- 

 men; western species 13 



9. Veins Rs and M in hind wing fused for one-fifth 



the length of the disc 10 



Veins Rs and M in hind wing fused for one-sev- 

 enth the length of the disc 12 



10. Top of head more black than yellow 11 



Top of head more yellow than black; male with 



a ventral apical lobe on abdominal segment 7 ; 

 subgenital plate of female very large and 

 broadly rounded expansa 



11. Yellow of the rear of the head extended forward 



into the ocellar triangle; rarely an extra r-m 



crossvein postica 



Yellow of the rear of the head restricted to a tri- 

 angle bordering the occiput and not extended 

 forward to the ocelli ; usually with an extra r-m 

 crossvein varians 



