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 is a small tributary of the East Fork of the Iron River in Bayfield County, Wisconsin. I visited it once and collected some bugs at road below a (former?) fish hatchery, but it looked too small to fish comfortably and I didn't try to catch anything.