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.
This specimen appears to be of the same species as this one collected in the same spot two months earlier. The identification of both is tentative. This one suffered some physical damage before being photographed, too, so the colors aren't totally natural. I was mostly photographing it to test out some new camera setting idea, which worked really well for a couple of closeups.
Attractor: Flies not designed to imitate any particular insect, but to incorporate characteristics attractive to trout. When trout aren't feeding selectively, attractors often outperform careful imitations as searching patterns because they are easier to see and incorporate more strike-triggering characteristics. They include legends like the Adams, Bivisible, and Royal Wulff.
This other word references the same concept: attractors.