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 is a very rare mayfly in western Montana. The shape of the last gill is a key to its identification. I have collected this species in only one location.
This mayfly was collected from the Upper Stillwater River in Montana on May 5th, 2007 and added to Troutnut.com by Bnewell on June 26th, 2011.