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.
I collected a female dun on the same day that probably belongs to the same species as this spinner. It keys pretty clearly to Epeorus pleuralis among the species given in the key in Taxonomy of Epeorus Frisoni (burks) And a Key to New England Species Of Epeorus.
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.