Note: Key for males only, and only to genus at present time.
1. Penes of male genitalia large, wide and flared; longitudinal veins brownish, crosseins dark; rare (listed by Randolph & McCafferty but not by OEPA). . . . . . . . Raptoheptagenia cruentata
Penes of male genitalia not as above; venation variable; widespread. . . . . . . . . . . . . . . . . 2
2. Stigmatic area of forewing with two to many anastomoses of crossveins; segment 1 of foretarsi one-third or less than one-third length of segment 2; femora usually with dark longitudinal streak or median spot. . . . . . . . . . . . . . . . . . . . . . . Rhithrogena manofesta
Stigmatic area of wing with or without anastomosed crossveins; if crossveins anastomosed then segment 1 of foretarsi half or more than half length of segment 2; femora usually without dark longitudinal streak (but variably shaped dark medial mark may be present). . . . . . . . 3
3. Forewings with two or ; basal b=crossveinsbthree crossveins below bullae (between veins R1 and R2) connected or nearly connected by dark spot, rarely only a dark spot present in membrane basal crossveins between R1 and R2 with dark margins. . . . . . . . . StenacronForewings may have crossveins below bullae darkened or slightly clouded, but never as above, crossveins between R1 and R2 rarely with dark margins. . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Penes of male genitalia distinctly L-shaped; segment 1 of foretarsi usually one-third to
two- thirds the length of segment 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Penes of male genetalia not distinctly L-shaped; segmetn 1 of foretarsi usually one-half the length of segment 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Posterior margins of abdominal terga III-VIII with dark median dot and lateral transverse submedian dashes; penes L-shaped. . . . . . . . . . . . . . . . . . . . . Stenonema femoratum
Posterior margins of abdomiinal terga III-VIII variable, but not marked as above; male penes stubby rounded L-shaped.. . . . . . . . . . . . . . . . . . . . . . . . . Stenonema (all other species)
6. Compound eyes of male separated by little more than diameter of one lateral ocellus; penes of male genitalia with large dorsolateral spines, discal spines absent. . . . . . . . . . Heptagenia
Compound eyes of male separated by three to five times the width of median ocellus; male genitalia not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Compound eyes of male separated on vertex by about the width of one compound eye; median titillators of male genitalia slender; penes of male genitalia with large dorsolateral spines and discal spines; crosveins between veins C and Sc usually margined with brown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leucrocuta
Key to the Genera of Heptageniidae Adults