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 was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
I collected this beautiful male Hendrickson specimen as a dun, along with a female Hendrickson from the same hatch. Both molted into spinners in my house within a couple of days.
One of the only real benefits I've got from my rearing aquarium so far is that I've had quite a variety of midges emerge, giving me a chance to photograph these fragile little insects which are otherwise really hard to transport in photogenic form. This one recovered from being gassed and flew away before I could photograph it on the ruler, but it was very small, around 1.5mm.
This female Hendrickson spinner is in kind of bad shape, but at least now I've got some good closeup photos of one. I collected her and a male Hendrickson as duns from the same hatch, and both molted into spinners in my house within a couple of days.