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 positively identified this specimen under a microscope with a good key. It was one of the more common species in a generally light mixed bag of mayflies over a big Catskill tailwater last night.
I swooped this one out of the air while it was mating with a female, so I can be certain about her ID as well.
This mayfly was collected from the West Branch of the Delaware River in New York on June 7th, 2007 and added to Troutnut.com by Troutnut on June 8th, 2007.