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t5f

Help with a mayfly nymph identification...

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I collected a couple of these nymphs last saturday the 7th, on the Bitterroot River near Darby, MT.

When I pick up rocks in the water one or two of these will by lying there, as soon as I touch them they go wild. Wiggling all over, trying to swim I think.

They are relatively big at approx .5 inches

taken out of water that was 37 F

 

I think they are some sort of swimming nymph, mayfly, but would like to hear your input on identification.

 

Thanks in advance!

 

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I would concur those are mayflies. sorry I can't seem to get further into the ID than that at the moment.

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J

 

I would say those bugs have the silhouette of crawlers. Based on colouration and size I would guess this species belongs to the Ephemerella genus (although most Ephemerella are smaller than your samples). Your photos are good. But not close enough to key out these mayflies.

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Thanks for your input!

 

i blew this picture up...maybe that will help? but it is a bit more blurry.

 

Any chance it's an Ameletus?post-19842-1236876411_thumb.jpg

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Futzer

 

My first guess was also Isonychia. The size is right. Three tails, etc. But the abdomen doesn't seem dark enough and I don't see that light dorsal stripe which is so characteristic of Isonychia. But I agree. It could be Isonychia. t5f: What species of Isonychia are endemic to Montana?

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I know you'd find both Slate Drakes and Mahogany duns in the area. I will have to do more homework to narrow it down.

 

Cheers, Jeff.

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t5f

 

There is an excellent chance these are Ameletus nymphs. According to Mayflies by Knopp and Cormier, most Ameletus species are found in middle-to-high altitude streams and rivers of the Pacific states. The size (10-13mm), colouration (light brown to dark, purplish-brown with conspicuous paler areas and darker markings), heavily-fringed tails with distinctive banding, banded legs, gill shape and placement, and large, compound eyes of the males (seen in your photographs) all indicate you may have several species of Ameletus nymphs in your bottle*. You might excuse us for not recognizing them: they are rare on East and Midwest waters, and only of minor importance on Western waters.

 

*Tail banding is :

alternate in A. cooki and A. oregonensis

middle band in A. sparsatus, A lineatus and A. ludens

absent in A. velox

 

At least one of your nymphs has a middle band and another has alternate banding.

 

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Ok, after your further input, which I appreciate very much! I am convinced that the correct mayfly is the 'brown dun' or ameletus. Futzer and BB75 I looked closer at the Isonychia mayfly and found the the gil shape on the Isonychia is quite a bit different that what I have collected. But...Good Guess.

Rockworm, thanks for including the note from the book by Knopp and Cormier. I found this online and looked closer at their description and am convinced that Ameletus is correct. Especially looking at the banding on the the tails and the gil plate shape. I was impressed that you caught on to the two different tails types. I missed that! Great Job.

 

 

Well, I belive the mystery is over.

I am going to throw away all of my new nymph creations now that you told me this Hatch is of only MINOR importance. :j_k:

 

Thanks again

t5f

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t5f

 

I wouldn't discard your nymph patterns. Since you now know where they live you also know where to fish them. Part of the reason they are considered of minor importance is because emergence occurs above the water. But in the west the nymphs are active year-round, are good swimmers, and emerge throughout the season. Therefore your fly has a good chance of catching trout if fished like an pre-emergent nymph. Let us know how successful you are.

 

 

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Rockworm, Thanks!

Here is a picture of the pattern I tied to try and match the nymph.

I will give it a try soon.

 

post-19842-1236964902_thumb.jpg

 

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I bent the hook for a more radical bend than a swimming nymph hook.

Hopefully it wont break!

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T5F, Nice Nymph, that will work great. Bending hooks should be fine. When I do, I heat them in the oven at 300°, then bend and shock in cold water. As long as the bend is not too far of an angle they will be fine. You might even try a jointed nymph due to their size.

 

Also, thanks for this post, it was fun trying to figure it out. Good Photos, Cheers, Jeff.

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