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'm calling this one Ephemerella dorothea infrequens because it was collected along with two males that positively ID to that species.
This mayfly was collected from the Madison River in Montana on July 1st, 2019 and added to Troutnut.com by Troutnut on July 18th, 2019.