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 female spinner was deceased when photographed, so the posture is unnatural, but it was a substantial hatch and clearly worth imitating (with wet flies to imitate the sunken ovipositing females) so I went ahead with the photos.
It was collected in association with a male spinner.
This mayfly was collected from Silver Creek in Idaho on September 4th, 2020 and added to Troutnut.com by Troutnut on September 18th, 2020.