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.
This species is very similar to Drunella flavilinea. In areas where their ranges overlap, they can sometimes be found in the same streams. They are similar enough that anglers sometimes refer to either or both species as "Flavs." Allen and Edmunds (1962) say that Drunella coloradensis tends to favor colder water than Drunella flavilinea and that it may emerge as much as a month later.
This one nicely illustrates the variation in coloration within an single Ephemerellid species in a single stream, when compared to its lighter, banded counterpart.