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'm not sure if this cranefly larva is in the genus Hexatoma or Limnophila, but the habitat suggests Hexatoma. Its coloring is iridescent, and I've never heard of that before. However, there is an insect virus genus Iridovirus which can infect craneflies and causes iridescence. It has not been reported in this region as far as I can tell, but perhaps it is the culprit. It makes for beautiful pictures.
This true fly was collected from Mongaup Creek in New York on April 19th, 2006 and added to Troutnut.com by Troutnut on April 21st, 2006.