The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
This specimen strikingly resembles another specimen from about 1300 miles away in the Catskills, which I tentatively called Ephemerella aurivillii. This one has much more prominent abdominal tubercles. It may be that they're both the same species and I don't have my identifications straight.
This mayfly was collected from the Long Lake Branch of the White River in Wisconsin on June 5th, 2005 and added to Troutnut.com by Troutnut on May 24th, 2006.