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.
Sounds to me like a drake - haven’t had the pleasure of fishing in CO, but around here they come in brown, gray, and green, depending on the stream / river and the time of year, and it is usually during the summer months.
We do get some large PMD’s around here, but I don’t think I have seen any I would consider a true size 12 dry fly, probably a sparse 14 at the biggest, and they definitely do not get into the gray range of color in this neck of the woods.
Right now we have a Western Green Drake hatch going on on one of my favorite cutthroat streams. Been fishing a size 12 extended body dry fly pattern, which the fish have been much liking, although they have not been particularly selective. Different water, different species.
If you go down to the Fly Tying Forum you will find a thread on the Western Green Drake. Will give you an idea of what has worked up here recently - and hopefully will again tomorrow.
Larry and John–thanks for your speedy replies. The elongated, very prominent tail in the photos you recommended closely resembles what I have been seeing. The photos of the “grey drake” show a darker speciment than we have here on the S. Fork, but the shape and size are the same, so the lighter coloration is probably a regional difference.
I will tie some this winter using moose hair for tails. I have been using 6-10 neck fibers, splayed, and they have worked well enough, but the moose hair would yield a much more realistic profile.
I would think gray drake also. If you go here: http://www.joshuabergan.com/images/photos/Fishing/Aquatic_insects/images1/ and scroll about a third of the way into it, there’s a pic of the gray drakes we have in sw Montana (you’ll probably just have to click on a few until you find the title grey_drake_gallatin…). Or maybe you’ll find something else there that resembles what you’re seeing. Around here, they’re almost a touch olive, and have slate wings with a prominent hind wing. And they’re meaty.
—sagefisher—