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 dun comes from the same location, and is about the same size, so is presumably the same species as this male spinner.
This mayfly was collected from Enfield Creek in Treman Park in New York on May 15th, 2007 and added to Troutnut.com by Troutnut on May 18th, 2007.