The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
Looking at this one under the microscope, I noted that is has untracheated gills which fork 1/3 of the way from the base and postero-lateral spines on abdominal segment 9
This mayfly was collected from unknown in Wisconsin on February 7th, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.