282 
Psyche 
[Dec. 
Iso genus Newm. 
This remains as used in Needham & Claassen. 
Hydroperla Frison 
This includes besides the species mentioned by Frison, 
varians, subvarians, hastata, guerini. 
Megahelus Klap. 
This is based on Isoperla hellona Bks. ; it has much 
resemblance to typical Isoperla, but the cubitus forks as 
in Isogenus. There are apparently one or two more 
species. 
Subfamily Isoperlinae 
1. Hind ocelli almost twice as near eyes as to each other, 
ocellar triangle fully twice as broad as long; pro- 
notum plainly more than twice as broad as long; 
spines under tibiae stout and long; small black spe- 
cies Nanoperla 
Hind ocelli not so near to eyes, and ocellar triangle 
not so broad 2 
2. Femora with distinct longer bristles among the 
shorter hair; cubito-anal cross-vein at end of the 
anal cell Perliola 
Femora with only the fringe of short, even hairs 3 
3. Hind ocelli looking laterally out over a broad, shallow 
groove toward eye or antenna; inner edge of ocelli 
scarcely above the middle surface ; mostly more or 
less marked with brown ; sometimes with extra cubi- 
tal cross-veins in hind wing W alshiola 
Hind ocelli looking more upward, inner edge usually 
a little above surface between ocelli; no shallow 
groove, at most a small, subtriangular pit just out- 
side of ocellus ; mostly pale species ; rarely with 
extra cross-veins in cubital area of hind wings. 
Isoperla 
Isoperla Bks. 
This I reduce to the forms similar to the genotype 
(bilineata) in having the cubitus forked so that the upper 
branch is continuous and the lower branch arising from 
