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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

This topic is about the Mayfly Species Ephemerella invaria

This species, the primary "Sulphur" hatch, stirs many feelings in the angler. There is nostalgia for days when everything clicked and large, selective trout were brought to hand. There is the bewildering memory of towering clouds of spinners which promise great fishing and then vanish back into the aspens as night falls. There is frustration from the maddening selectivity with which trout approach the emerging duns--a vexing challenge that, for some of us, is the source of our excitement when Sulphur time rolls around.

Ephemerella invaria is one of the two species frequently known as Sulphurs (the other is Ephemerella dorothea). There used to be a third, Ephemerella rotunda, but entomologists recently discovered that invaria and rotunda are a single species with an incredible range of individual variation. This variation and the similarity to the also variable dorothea make telling them apart exceptionally tricky.

As the combination of two already prolific species, this has become the most abundant of all mayfly species in Eastern and Midwestern trout streams.

Example specimens

Martinlf
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Palmyra PA

Posts: 3047
Martinlf on May 19, 2009May 19th, 2009, 2:54 pm EDT
OK, this is going to seem like a major duh experience for some of you, but the other night I found a sulphur spinner on the door of a bathhouse in a campground I was staying at. Looking for other bugs I then saw a pale nymph shuck on the door. I was totally confused. A nymph this far from the stream? Was this some alien bug? Looking closer I noticed that the shape was too slender for a nymph and that the wing pads were more like little protruding pockets--and it hit me. Spinner shuck. I knew that mayflies molted to produce a spinner, but I had thought the shuck would be more insubstantial--something that would be flimsy and lack form. This was so cool, and at the same time I felt so silly for thinking it could somehow have been a nymph shuck. It's the first spinner shuck I've seen, but I assume that I'll start seeing them everywhere now, like a new word you learn. Anybody else have a spinner shuck story?
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
Konchu
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Site Editor
Indiana

Posts: 498
Konchu on May 19, 2009May 19th, 2009, 3:32 pm EDT
Worked a Caenis hatch in the Dakotas and came away covered in shucks. They were using our shirts to land and molt. It was amazing.
Shawnny3
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Pleasant Gap, PA

Posts: 1197
Shawnny3 on May 20, 2009May 20th, 2009, 12:14 am EDT
Nice story, Louis. The "duh" moments in my flyfishing experience are too numerous to mention.

-Shawn
Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
www.davisflydesigns.com
Wiflyfisher
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Wisconsin

Posts: 622
Wiflyfisher on May 20, 2009May 20th, 2009, 12:34 am EDT
I think you mean a "dun shuck" when molting into a spinner, not a "spinner shuck"

I see a lot of shucked mayfly dun skins on our screened in porch at the lake. Hex. limbata skins all over the place at times when the hatch is heavy.
Martinlf
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Palmyra PA

Posts: 3047
Martinlf on May 20, 2009May 20th, 2009, 1:46 am EDT
Good point, John. Thanks for the clarification.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
Shawnny3
Moderator
Pleasant Gap, PA

Posts: 1197
Shawnny3 on May 20, 2009May 20th, 2009, 12:36 pm EDT
You calling Louis a "dun shuck", John? This forum has an interesting way of getting people riled up.

Regardless of how the term was intended, I think it should become a new fishing expletive. I know I'm going to say it loudly to myself the next time I flip my leader into a tall tree.

-Shawn
Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
www.davisflydesigns.com
Troutnut
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Bellevue, WA

Posts: 2758
Troutnut on May 20, 2009May 20th, 2009, 9:23 pm EDT
I can see the hit movie now! A passenger jet flies through a massive Hex hatch, and it's up to Samuel L. Jackson to save the passengers and the engines from millions of mayflies. Near the end of the movie he finally gets really angry and proclaims, I have had it with these dunner-shucking drakes on this dunner-shucking plane!
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Wiflyfisher
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Wisconsin

Posts: 622
Wiflyfisher on May 20, 2009May 20th, 2009, 11:31 pm EDT
Well, I was "dun shucked" when Louis said he saw a "spinner shuck".

Shawn, when I backcast my fly & leader into the tree I have better, more choice words to mumble to myself, but dun shuck might fit the bill too.

Jason, now you can make a new t-shirt or coffee mug over at Cafe Press that says: "I am a dun shuck".
Geezer
Guelph, Ontario

Posts: 2
Geezer on Jul 24, 2009July 24th, 2009, 4:48 am EDT
Okay, the "Drakes on the Plane" reference was pretty 'effin' funny, Troutnut. I actually laughed out loud about it.
Ericd
Mpls, MN

Posts: 113
Ericd on Jul 24, 2009July 24th, 2009, 9:31 am EDT
Oh boy, that is funny.
I can't wait to add this new expletive to my fishing. My friends already shake their heads at "frelling," "fracking," and "gorram."
Martinlf
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Moderator
Palmyra PA

Posts: 3047
Martinlf on Jul 24, 2009July 24th, 2009, 1:23 pm EDT
Now I'm figuring out what those white husks are on the water in the middst of the Trico hatch. I'll be dun shucked again--they're the spinner shucks!
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell

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