The reason I focused in on Drunella is that the body color, dark wings, stout thorax, steeply tapered abdomen, and husky femora sure looked right to me. I knew I was out on a limb here with only these photos to work with so I applied my Grandpa's admonition, "If you're gonna be wrong, at least don't be meek about it!" :) Without a good look at the special parts, it's pretty tough; but there are still a few clues discernible from the photos that are worthy of more fun discussion - though I'm not sure if they provide more clarity or more confusion.:)
Eric - I don't think they're Attenella. Besides being too big, they're the wrong body shape and the femora don't look right (real scientific, I know:)). They're also missing mesonotal projections. I've never seen them mentioned (not that my memory has proved trustworthy), but they usually seem to show up on the specimens of Attenella duns I've seen. I haven't seen many photos of Dannella and descriptions are pretty sparse, but from what I can glean, they are stocky like drunella, sized in the 7mm range, dark or blue winged, and usually olivaceous.
Luke - Dannella, huh? I must admit the possibility never crossed my mind. Should have picked up on your posterolateral projection and habitat comments, but at the time I didn't see anything extraordinary about them and my memory failed me regarding their mention as a key character of Dannella in Merritt. The puzzle is I've seen the same looking projections on other ephemerellids (including cornuta) as appear in these photos. Since I can't make out the presence or absence of gill sockets, I don't know how definitive this character is here. It's interesting that projections on ephemerellids sometimes look to be lacking while in another photo of the same critter they stand out like the German beach fortifications at Normandy. It depends on the angle of the photo and flex of the body, I guess. Anyway, that's why I asked you to expand a little on this issue.
BTW - looking closer at the male's forewing, the sparseness of crossveins between the costal and subcostal together with the crowding of the subcostal and radial sure looks like a good match for Dannella, but maybe they're just obfuscated. Diagrams I can find of the hind wings don't show the prominent costal projection as in this photo. This raises another question. I seem to see a lot of ephemerellid hindwing diagrams lacking projections and I'm not sure they're accurate. Are you aware of any reason for this discrepancy?
Sorry for all the questions, I can't help myself...:)
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman