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 haven't keyed this specimen out, but I am instead placing it in Hydropsyche based on the striking visual similarity to this one, which I did key out.
This caddisfly was collected from the Madison River in Montana on June 30th, 2019 and added to Troutnut.com by Troutnut on July 17th, 2019.