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.
This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
Litobrancha on Sep 5, 2006September 5th, 2006, 8:38 am EDT
Wow! Looks like Himalopsyche, a Rhyacophilid we don't get down here. World checklist has one Nearctic species, H. phryganea. Quick note, Himalopsyche fifth instars are huge and supposed to have thoracic branched gills too. Not sure what other Rhyacophila larvae have abdominal gills, in the SE USA only R. brunnea does and i've never seen it. Great photo!