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.
Key characteristics verified under the microscope:
-The head has 3 ocelli.
-Maxillary palp has 5 segments, with the second segment rounded. In some of the pictures it looks like 6 with the 3rd segment rounded, but the basal "segment" in that case isn't part of the palp.
-Foretibiae lack preapical spurs.
-Pronotum with mesal setose warts widely spaced.
All of this very clearly indicates Glossosomatidae. Beyond there:
-The tibial spur counts (fore / middle / hind tibiae) are 2, 4, and 4.
-From the pictures, the hind wing discoidal cell is closed, not open. Subfamily Glossosomatinae.
-The upper and lower parts of the mesepisternum are separated by a constriction, not a transverse suture. Microscope picture included.
This leads to a very confident genus ID of Glossosoma. I don't have the information to take it to species.