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 Nelson, C.R. & Baumann, R.W. (1987) New winter stoneflies of the genus Capnia with notes and an annotated checklist of the Capniidae of California (Plecoptera: Capniidae). Entomography 5, 485–521.