The lid is a standard size pickle jar lid, to give you scale. This was a good sized "blue wing olive" - but not the usual I'm used to seeing as it had three tails. It was also fairly large, a solid #16 or slightly larger. The dun wings were, as you can see, pretty large as well. Can you precisely identify this one? And, turning over rocks revealed a number of immature nymphs. This one, however, seemed to be ready-to-go with a wing case that was looking like it was darkening. I was thinking Ephemerella, but it doesn't seem elongated enough and had more pronounced gills than I'd have expected based on images I've seen. The width of the head, pronounced eyes, and the pronounced gills now have me thinking it is some sort of Epeorus (yellow quill) - and there were in fact good sized yellow mayflies coming off at about a size 14 that I was thinking may very well be yellow quills. So, how about this nymph?