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 Smith, L.W. (1917) Studies of North American Plecoptera (Pteronarcinae and Perlodini). Transactions of the American Entomological Society 43, 433–489.