24 THOMAS SAY FOUNDATION 
ments; licinia with a fringe of hairs below the second 
Loothe. ols pala MS ae eee at ene ae 10 
10. A distinct occipital ridge extending transversely across the 
head from the posterior margin of one eye to the other’ 
Bee Lee a Rae ea te Gill bearing Perla (p. 46) 
wer No occipital ridge present; mostly strikingly patterned 
“ nymphs Acroneuria (p. 80) 
© 
vn 11. Very small, inconspicuous, single, finger-like gills at the outer, 
base of the submentum, and sometimes also on the lateral 
margins of the thorax between the bases of the legs.... 
poo he SRR oan OSS af te antes Senin eae ie eno Perlodes (p. 41) 
No gills on submenttim 2). .0-.00. 202... eee 12 
12. Head very long, squarish; eyes small and set far forward so 
that the distance from the hind margin of the eye to the 
posterior border of the head is much greater than the 
diameter of the eyés.a. a. eee Paraperla (p. 64) 
Head not strikingly long; distance from the hind border of 
the eye to the posterior margin of the head not much more 
than the diameter of the eye ........ 2.2) 13 
13. Very wide through the wing pads and with the lateral mar- 
gcins of the pads broadly rounded; lacinia unidentate ; 
maxillary palpus with the first four segments about equally 
large in diameter, but with the apical segment strikingly 
slender and the tip of the fourth segment somewhat pro- 
duced beyond the base of the apical segment?........... 
scien tlde le Ronda or Alloperla and Chloroperla (p. 58 and 63) 
Not exceptionally wide through the wing pads; lateral mar- 
gins of wing pads straight or sinuate but never broadly 
rounded; lacinia bidentate, or, if unidentate then the galea 
is much reduced and less than half as long as the lacinia; 
apical segment of maxillary palpus not strikingly thinner 
than the previous ones, although the segments are succes- 
sively. reduced#in. size..h...0....054...05 40 14 
* Acroneuria ruralis and A. depressa will also key out here since they 
each possess a distinct occipital ridge. However, A. ruralis will be recognized 
by its nearly uniform light brown color, the wide pronotum with wide 
flanges, and the long cerci which are longer than the body. A. depressa is a 
Western species, possesses anal gills and therefore could be confused only 
with P. capitata from which it differs greatly in color pattern, as shown in 
the illustrations of these two species. 
* Chloroperla which has only one species, cydippe, can not easily be 
separated from Alloperla but in Chloroperla the anterio-lateral angles of 
the submentum are not produced beyond the mentum while in the Alloperla, 
ieee are known, they are produced to, or nearly to, the base of the labial 
palpi. 
