The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
I'm guessing this is an immature Peltoperla, because it lacks the well-developed setal fringe on the hind femora that would indicate Tallaperla, but it also lacks the dark spots that should indicate a mature Peltoperla nymph.
This stonefly was collected from Mystery Creek #62 in New York on April 1st, 2007 and added to Troutnut.com by Troutnut on April 3rd, 2007.