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. & Nelson, C.R. (1994) Systematics, phylogeny and zoogeography of genus Yoraperla (Plecoptera: Peltoperlidae). Entomologica Scandinavica 25, 241–273.