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.
I spent ten mid-October days in central Idaho almost-but-not-quite getting shots at mule deer bucks, and at one point I found a free evening (the 17th) to wet a line in the famous Nature Conservancy stretch of scenic Silver Creek. I don't know that I've ever seen so many fish, especially nice fish, in one place. That explains why so many other anglers were also there on a very windy October afternoon.
However, the conditions were tough and my skills weren't quite up to the task. Strong wind ripped relentlessly through the valley, suppressing insect activity as well as making stealthy casting a challenge. Fish occasionally rose to tiny BWOs, but only a handful rose consistently. Trying various techniques, I missed some strikes and caught one small brown.