Yesterday, I hit the Rivanna at Crofton: today, it was a small stream in Sugar Hollow. And, at both streams I found much the same thing: common stoneflies, Acroneuria abnormis in both cases, and flatheaded mayflies -- but not the same species. In the photo above, the "brown" form on A. abnormis. So, so broad, a very unusual shape. But it made for some very good photos.
And the flatheads I found in the Rivanna were -- like those in Buck Mt. Creek -- Maccaffertium modestum.
Different habitat, different results. In Sugar Hollow today, it was the "patterned" form of A. abnormis.
And the flatheads out there were Maccaffertium pudicum, a species with a much different tolerance value (2.1 vs. the 5.7 of M. modestum).
And there were Goera larvae (weighted case-makers) in our small mountain stream.
But the story at the moment seems to be Acroneuria stones and Maccaffertium flatheads. Things will be changing real soon.