Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
As usual, I reserve the right to be completely wrong.:)
There were enough of these flitting around in the evening to keep the fish looking up. Anglers can easily confuse these with Dicosmoecus species (October Caddis) at this time of year, but their wings are quite different and they like gentler flows.