"I am convinced ... due, in part, to the tight clustering of cross veins near the bulla in combination with the dark marks along the rear of the abdominal tergites. Although only the right-side and the center sets of femoratum’s distinctive “tripunctate” markings can be seen in [this] specimen and only the left-side set can be seen in(1), these markings could only be confused for the “bipunctate” marks of Maccaffertium terminatum terminatum (which now includes the concept of “bipunctatum” as a synonym in much the same way that femoratum includes “tripunctatum”). That species not only looks different, but it lacks the tight cluster of cross veins in the forewing."
Moved from Maccaffertium.

Moved from Mayflies.
Thanks Roger.

Tom-

Very nice photo of a Maccaffertium male imago.