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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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Lateral view of a Female Procloeon (Baetidae) (Tiny Sulphur Dun) Mayfly Dun from Enfield Creek in New York
This dun of a fairly large Baetidae species was one of only a couple I saw all evening.
Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on Aug 27, 2006August 27th, 2006, 5:55 pm EDT
Jason-

My belief is that Plauditus, Pseudocloeon, and Procloeon are the Baetids absent hind wings, whereas Centroptilum (among the others) has minute hind wings. If I am correct, then given the choice you posed, that would make your specimen Centroptilum. This is (of course) strictly based on my having successfully digested the "available literature", and as I remember, there was a bit of inconsistency between authors in that area, so I probably chose to believe whichever one (or ones) I believed to have more credibility. Does any of this sound familiar?
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Troutnut
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Bellevue, WA

Posts: 2758
Troutnut on Aug 27, 2006August 27th, 2006, 6:20 pm EDT
If I'm reading the key in Merritt & Cummins correctly, Procloeon can have hind wings present or absent. I think the angling literature is based on older sources, and the species were shuffled around a lot since the publication of most of those books.

I tried to find a paper on Procloeon identification on the FAMU site without any luck. I guess I'll have to spend some time in the Cornell library this winter for this one.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Entoman
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Northern CA & ID

Posts: 2604
Entoman on Jul 13, 2011July 13th, 2011, 1:39 pm EDT
Jason & Roger-

Boy, this is another example of the value of your updates to the site Jason. Related Topics pulled this topic up and even though it is almost 5 years old, it has important relevance to the current discussions we're having about the genus Centroptilum.

Though the difficulties in place 5 years ago are still in play for the baetids, luckily the presence of single intercalaries and hind wings reduces the possibilities to two genera, Centroptillum and Procloeon.

Besides the shuffling of species among genera, to call morphological information on their females scant is an understatement. Looking at the males, there is one species I'm aware of sized this large and with hind wings this severly slender (described as more than 6 times long as wide) that also has the spurs (curving spikes) and a NY distribution. It is also one of those that "stayed home" in Centroptilum. In the old nomenclature it was referred to as C. convexum. It is now considered synonymous with C. album, which is where I'd place this specimen. Hopefully somebody will be able to supply better information now or in the future, but this is such a beautiful example of the look, I'll move it there if you concur.

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
Entoman
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Northern CA & ID

Posts: 2604
Entoman on Jul 13, 2011July 13th, 2011, 2:56 pm EDT
Follow up-

I forgot to adequately address the elephant in the room, which is the size of this critter. 7mm is definitely outsized for most species of Centroptillum and all the species of Procloeon that I'm aware of. Your specimen's size is probably a better indicator for album than hind wing conformation since it's female. There is another synonym of C. album, the prev. C. walshi that has been documented to attain this size and even larger.
"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
Oldredbarn
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Novi, MI

Posts: 2600
Oldredbarn on Jul 14, 2011July 14th, 2011, 9:37 am EDT
I don't want to in any way distract from your discussion on the placement of this one, but what a gorgeous bug! The photography is wonderful, but I wonder a bit on the lighting and its effect on its "true" color. But you can't beat the available detail etc.

In the photo of its underside what's going on there in the area of the thorax? It appears to be bubbles you can see inside it. Thats not eggs that far up is it?

Spence
"Even when my best efforts fail it's a satisfying challenge, and that, after all, is the essence of fly fishing." -Chauncy Lively

"Envy not the man who lives beside the river, but the man the river flows through." Joseph T Heywood
Entoman
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Northern CA & ID

Posts: 2604
Entoman on Jul 14, 2011July 14th, 2011, 11:09 am EDT
Hi Spence,

One of the fascinating things about macro-photography is the view it gives us of such fine details. Though they look like interior bubbles, they are actually chitinous little bumps or rings that are common on ventral surfaces of mayflies. They are definitely not eggs.

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
Troutnut
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Administrator
Bellevue, WA

Posts: 2758
Troutnut on Jul 14, 2011July 14th, 2011, 1:06 pm EDT
Okay, I've moved this one into Centroptilum album for now.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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