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 is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).
GONZO on Sep 9, 2008September 9th, 2008, 1:01 pm EDT
I don't think this is Isoperla or even a perlodid. The little perlids of the genus Perlesta are frequently mistaken for Isoperla. Although there are a few exceptions, most Eastern Isoperla are spring or early summer emergers. Perlesta tends to be more of a summer emerger. In general appearance, the amber, brownish, or blackish wings with yellow borders are common to many Perlesta species. The nearly concolorous pronotum (often with a similar rugose pattern) and the variable darkening of the ocellar triangle are also typical of many species in this genus. Looking closer, the third photo shows long bristles along the lower front edge of the forefemur. As far as I know, these bristles are found in perlids and chloroperlids, but not in Isoperla.