The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
I'm unsure of the ID on this one; keys put it closest to Cinygmula reticulata, but I'm very doubtful of the species and not positive on the genus. Epeorus is another possibility, but I don't know which species it would be.
This one was collected in association with a female dun probably of a different family.
This mayfly was collected from the South Fork Stillaguamish River in Washington on July 1st, 2017 and added to Troutnut.com by Troutnut on July 2nd, 2017.