The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
This is the most widespread species of Ephemerella, and also the most abundant in some places, but nobody I've talked to seemed to know what its duns looked like, and there were no pictures of its duns online or in any angling books. That mystery is solved with this male dun, which hatched from a definitively identified nymph.
This mayfly was collected from Nome Creek in Alaska on July 10th, 2011 and added to Troutnut.com by Troutnut on July 12th, 2011.