Ephemerella subvaria (Hendrickson) Mayfly Nymph Pictures

I found a few of these this spring in just one small Finger Lakes tributary, mixed in with various normal-looking E. subvaria nymphs. The unusual characteristic is the pale prothorax -- the "white collar" segment just behind the head. I've never heard of that color configuration before. Has anyone else?

Maybe they're mayfly clergy...

This photo shows the light band on the top of the subvaria nymph. The lighter collar seems to be abnormal, or at least an unusual color variation, if I remember the previous discussion on this photo.

I just noted the photo of the bug's belly. It appears solid brown, much to my surprise. Hmm. . . Gonzo? I believe he's away for the holidays, but I'll be interested in his answer on imitating this and other nymphs.

I've navigated away from the photo of the subvaria's underwater on the rock, but they are awesome too.