Name of grey mayfly?
Starting about a week after S. Fork of the Rio Grande in CO. became fishable at beginnng of July., a size #12 grey mayfly (w/elongatated tail giving it a total length of 1.5 inches or so) started coming off about 1 p.m.
The emergence came progressively earlier in the day for about three weeks and then dropped off, at least to the pt. where big trout weren't rising to them. When the dun of this fly was on the water, the trout went crazy and were highly, highly selective--something pretty rare on this relatively small stream.
Some people have told me this fly is a PMD, but there are PMD and evening duns here now that are much smaller i.e., 18-24,while there are still a few of these large mayflies present. I don't see them coming off during the day, but I do see their spinners each evening in a mating dance over the riffles.
I found the fly in a local shop and it was simply labeled "Grey Mayfly." The Pal Morning duns and Pale evening duns the shop carries are of #18 and smaller.
My question: Is this grey mayfly a PMD or does it have another name?
Thanks in advance for your help.
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