152 Inuinors NaturaAt History Survey BULLETIN Vol. 26, Art. 1 
<EY TO GENER: relatively undifferentiated, elongate or 
sppiabiheandiben sear stubby ee: fig. 391.) +,././c sees 
AbuLT MALES th ea ee ea 46. Rhithrogena 
1. Fore tarsus not more than three-fourths Stigmatic crossveins of fore wing not 
as long as fore tibia....47. Anepeorus anastomosed, or only partly so, as in 
Fore tarsus longer than fore tibia. ...... 2 fig. 319, or anastomosed and forming 
2. Vein Ry, of hind wing unbranched, fig. two rows of cellules, as in fig. 322; penis 
=, ep ces _.......48. Arthroplea lobes variously modified, with lateral 
Vein Ry,s of hind wing forked at or near or apical expansions, figs. 331-356, 363— 
center of wing, figs. 317-320........ 3 380, 389... 68. 0 5 
3. First segment of fore tarsus as long as or 5. Penis lobes divided to base or fused on 
longer than second....... 43. Epeorus meson at base only, fig. 388.......... 
First segment of fore tarsus shorter than biainitseo 3 < pts aug ee 44. Cinygmula 
Fe, Sa eee REN a ied Stn Phar aan 4 Penis lobes fused on meson for at least 
4. Stigmatic crossveins of fore wing anasto- their basal halves, figs. 331-356, 363— 
mosed, figs. 320-323; penes a pair of 380,389... «.:::sfean ae 6 
ase, WS NY Dae oo Be A 
©, 
=. IELTS 
BERG 
SSP 
iS 
L? 
Cal 
ES) m, Rs 322 
Cu, 
32l 
Fig. 317.—Stenonema canadense, wings. 
Fig. 318.—Heptagenia maculipennis, wings. 
Fig. 319.—Epeorus pleuralis, wings. 
Fig. 320.—Rhithrogena morrisoni, wings. 
Fig. 321.—Arthroplea sp., wings. (After Blair.) 
Fig. 322.—Cinygma integrum, stigmatic area of fore wing. 
Fig. 323.—Rhithrogena morrisoni, stigmatic area of fore wing. 
