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.
I found this nymph wriggling in the surface film during a hatch of related Strophopteryx adults. This nymph died in transport so it's not alive in the photos, but it's pretty close to its live colors.