Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
In 13 records from GBIF, adults of this species have been collected during August (31%), October (23%), April (15%), September (8%), June (8%), May (8%), and July (8%).
In 2 records from GBIF, this species has been collected at elevations of 4170 and 5200 ft.