The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
I'm just guessing Neoleptophlebia instead of Paraleptophlebia on this one because I tended to find more of their nymphs in the area, but take that with a grain of salt.
This mayfly was collected from the West Branch of the Delaware River in New York on June 1st, 2007 and added to Troutnut.com by Troutnut on June 4th, 2007.