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 looked at this nymph closely under a microscope to ascertain some key features I was wondering about in previous photographs of similar specimens. It definitely does have the fan-tail characteristic of the Ephemerella genus. It also has strongly 2-banded tibiae and definite tiny abdominal tubercles.
This mayfly was collected from unknown in Wisconsin on February 7th, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.