Most of these genera do not have keys yet so the link goes to an introduction for the genera.
| 1a. Femora ususally with dark longitudinal streak near middle. Stigmatic area of wing with two to many anastomoses of crossveins. Basal segment of foretarsi less than or equal to one-third the length of segment 2. | |
| 1b. Femora usually without dark streak.Stigmatic area of wing with or without anastomosed crossveins. If crossveins anastomosed, basal segment of fore tarsi equal or longer to half of segment 2. | |
| 2a. Foretarsal segment 1 equal or longer than segment 2. | |
| 2b. Foretarsal segment one 4/5ths or less than segment 2. | |
| 3a. Penis lobes separated or appearing separated to near base medially. Basal segment of foretarsi usually 2/3 or more the length of segment 2. | |
| 3b. Penis lobes fused medially at least in basal half. Basal segment of foretarsi 2/3 or less the length of segment 2, usually less than half the length of segment 2. | |
| 4a. Eyes of male meeting on vertex or separated by less than the diameter of the median ocellus. | |
| 4b. Eyes of males separated dorsally by at least the width of one lateral ocellus. | |
ReferencesWaltz,RD; Burian,SK 2008 Ephemeroptera. In: An Introduction to the Aquatic Insects of North America. 4th ed. Eds: Merritt,RW; Cummins,KW; Berg,MB Kendall/Hunt Publishing Company, Dubuque, Iowa, 181-236.Brown, Wendy S. 2004 Mayflies (Ephemeroptera) of Gunnison County, Colorado, USA www.gunnisoninsects.org |