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 specimen is in the genus Acerpenna because of the very sharp costal process on her hind wing. I'm guessing pygmaea because it is the most common species.
Editor note: Not Acerpenna. This is most likely Baetis. See comments on this male specimen for rationale. Also compare with the female specimen associated with it.
This mayfly was collected from the Bois Brule River in Wisconsin on July 1st, 2005 and added to Troutnut.com by Troutnut on April 22nd, 2006.