This is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).
These are very rarely called Gray-Winged Blue Duns.
This is the most common Caenis species in our trout streams. It is often found in angling books under a former name, Caenis simulans. Trout occasionally feed on it selectively.