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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Redacted
Posts: 5
Redacted on Feb 14, 2011February 14th, 2011, 4:07 am EST
Bitterroot River near Missoula, Montana. Late March emergence.
PaulRoberts
PaulRoberts's profile picture
Colorado

Posts: 1776
PaulRoberts on Feb 14, 2011February 14th, 2011, 6:21 am EST
That early? Very cool.
Redacted
Posts: 5
Redacted on Feb 15, 2011February 15th, 2011, 6:14 am EST
Paul,
Ment to put up a photo for people to ID, but for some reason can't get it to work before the post floats away.

Anyway, yes, this early mayfly provides some of the very best fishing of the season. It is big enough (well matched with a #14 although it looks larger floating on the surface) and numerous enough to move the fish to a frenzy sometimes.It generally follows the famous Skwalla emergence, although there is considerable overlap. Once runoff starts in ernest, though, the fun is over.

An article I wrote for Tom Chandler's Troutunderground.com blog last spring has pictures of Skwallas copulating (note the atrophied wings of the male) and a really nifty picture of the mayfly in question.

Just do a search for "Sully" and look for that post to see those pictures since I'm too stupid to figure out how to do it directly.

PaulRoberts
PaulRoberts's profile picture
Colorado

Posts: 1776
PaulRoberts on Feb 15, 2011February 15th, 2011, 7:02 am EST
Put your images in a host site, like Photobucket, and then copy it in.

Use the
(User tried to post an image here without an source.)
format, but for this site you need to change the IMG to lower case -img.



changes to:



Why do you think it's Ameletus? It looks like a bright Rhithrogena morrisoni. Have you keyed it? Hind wing is large like Rhithro. And the abdomen appears pretty short, for Ameletus. Not certain of course, just wondering.

I do have an Ameletus dun photo in my collection, but it's a transparency. I tried to take a point-n-shoot of it, but the result was just lousy. It's an eastern species (ludens I think) and the stamp on the slide is April(!). They do have a long emergence period -like all summer. I guess I forgot how early they can start. It is a leaden gray throughout, including wing. Looks a lot like a slim Siphlonurus, and a lot like an Isonychia.

At least some western Ameletus have marked wings from what I've read, and I tried to photo one last summer, with marked wings -and almost succeeded! I was keeping my eyes open for them and had one land on my hat brim. Did look like a slim Rhithro. Will keep my eyes open in the future.
Redacted
Posts: 5
Redacted on Feb 16, 2011February 16th, 2011, 4:44 am EST
Thanks Paul.
PaulRoberts
PaulRoberts's profile picture
Colorado

Posts: 1776
PaulRoberts on Feb 16, 2011February 16th, 2011, 6:27 am EST
Another thing: Look at the width of the femur. That's Rhithrogena.
Entoman
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Feb 16, 2011February 16th, 2011, 7:11 am EST
Hi Redacted,

Paul is right. They usually appear darker, but lighting in the photo could be the reason for that. Ameletus is a large swimmer whereas Rhithrogena is a clinger. Keys aside,the body and wing conformation is very different between the two (as are the fishing methods and flies required). Both share similar coloration and mottling (or lack of) and can be easily confused depending on the angle and quality of the photograph. But even without a photograph, the real clue is your mention of hatching in the early Spring. Skwalas and W. March Browns are two favorite hatches on one of my local rivers (mid FE through MA). The lack of precip. in JA and early FE was setting up a banner year! I was just getting geared up and now its starting to rain... Much higher levels and off color to flat out muddy if it goes on much longer! Supposed to be socked in all week which is dimming my hopes for this years Skwala/M. Brown tag team. Once the storm window opens out here it can last for weeks....(sigh) Check out my comments on Skwala, you might find them enteresting... BTW, great photo of the March Brown! Can you share some photos of the Skwala Adult/Nymphs from your river if you have them?

Best regards,

Kurt
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman

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