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.
A few of these larger stoneflies were fluttering around the South Fork on an evening dominated by much smaller species.
This one has been difficult to identify. I can't spot any of the gill remnants characteristic of Perlidae, but the wing venation seems to point in that direction. I tried keying it out as Perlodidae but arrived at Isoperla, every western species of which has significantly smaller bodies than this one.
Edit: See forum comments for a likely correct identification.
This stonefly was collected from the South Fork Snoqualmie River in Washington on July 20th, 2019 and added to Troutnut.com by Troutnut on July 22nd, 2019.