The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
These species hatch in or near the surface in calm water. Emergence is quite fast, but the duns may drift a while.
Spinner behavior
Time of day: Dusk
Habitat: Riffles
The female spinners oviposit by flying over the water and dropping down to the surface to release some eggs, then taking off to do it again. They eventually fall spent.