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 Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.
Described by Stark, B.P. & Surdick, R.F. (1987) A new Kathroperla species from western North America (Plecoptera: Chloroperlidae). Proceedings of the Entomological Society of Washington 89, 527–531.