Male Maccaffertium modestum (Cream Cahill) Mayfly Dun Pictures

Hi Jason-

While scanning the Stenacron specimens in response to Jeff's question, I came across this one. It does not appear to be Stenacron. It lacks the dark pigmentation (spot) between R1 and R2 that is distinctive of this genus. Clearly, it is a member of the Heptageniidae, but I haven't found a definitive clue to indicate which one it might be. Perhaps someone else will detect something more conclusive.