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 one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.
I spent most of the month of May in Alaska, and most of that sitting in an AirBnB in North Pole abiding by the required 2-week indoor quarantine for travelers from out-of-state due to Covid-19. After the quarantine came a frantic sequence of fieldwork to train the technician we hired to complete our second summer of data collection on a study of food resources for juvenile Chinook Salmon in the Chena River. However, our weather-dependent sampling schedule allowed for a break from May 29th-31st, and I drove south to chase rainbow trout.