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.
Notes from the microscope on the ID: Maxillary palp is present, distinctly 2-segmented, but very small. Gills on segment 4-7. This specimen has some unfortunate damage to the abdomen, but it's the only one I found in my sample.
This mayfly was collected from the East Fork Big Lost River in Idaho on August 3rd, 2020 and added to Troutnut.com by Troutnut on August 19th, 2020.