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.
In Baumann's Stoneflies of the Rocky Mountains, this specimen keys to Sweltsa fidelis, but the number of species in that key is fairly small and it might not be accurate.
This stonefly was collected from the Madison River in Montana on June 30th, 2019 and added to Troutnut.com by Troutnut on July 17th, 2019.