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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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Millcreek has attached these 7 pictures. The message is below.
Isoperla marmorata. In alcohol. 14mm (excluding cerci).
Isoperla marmorata. In alcohol. 14mm (excluding cerci).
Isoperla marmorata. In alcohol. 14mm (excluding cerci).
Isoperla marmorata. In alcohol. Ventral view of head.
Isoperla mormona. In alcohol. 8 mm (excluding cerci).
Isoperla mormona. In alcohol. 8 mm (excluding cerci).
Isoperla mormona. In alcohol. 7 mm (excluding cerci).
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Sep 3, 2014September 3rd, 2014, 11:10 am EDT
These two Isoperla nymphs are common in the Russian River in the early part of the year (late January to mid April). As far as I can determine they're Isoperla marmorata and Isoperla mormona. I used Merritt, Cummins and Berg as well as "Nymphs of North American Stonefly Genera" by Stewart and Stark to identify the nymphs to genus. I used Sandberg's "The Isoperla of California (Plecoptera: Perlodidae); Larval Descriptions and a Key to 17 Western Nearctic Species" to identify them to species. http://www2.pms-lj.si/illiesia/papers/Illiesia07-22.pdf .

Sandberg's key is for male larvae and the photos of Isoperla marmorata shown here are female but identification was made with male specimens.

All specimens were in alcohol but the photos were taken within 12 hours of collection so the coloration is accurate.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Oldredbarn
Oldredbarn's profile picture
Novi, MI

Posts: 2600
Oldredbarn on Sep 3, 2014September 3rd, 2014, 2:27 pm EDT
Nice pics! If you have it, could you give us a ball-park measurement on these?

Thanks!

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
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Sep 3, 2014September 3rd, 2014, 6:28 pm EDT
Nice pics! If you have it, could you give us a ball-park measurement on these?


Spence, The measurements are in the captions under the photos. 14 mm for I.marmorata and 7-8 mm for I. mormona. The measurements are for body length and don't include the cerci.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Oldredbarn
Oldredbarn's profile picture
Novi, MI

Posts: 2600
Oldredbarn on Sep 3, 2014September 3rd, 2014, 8:40 pm EDT
How did I over look that?!

Thanks.
"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
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Sep 3, 2014September 3rd, 2014, 10:27 pm EDT
Thanks for the link, Mark. Going beyond genus with Stoneflies and Caddis is often much more difficult as access to the literature is not easy or cheap. Kudos for sharing. Stones are especially fun as many if not most have determinative characters that can be identified in photos.
"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
Millcreek
Healdsburg, CA

Posts: 344
Millcreek on Sep 4, 2014September 4th, 2014, 6:57 am EDT
Thanks for the link, Mark


You're welcome. It is harder to find literature on Plecoptera or Trichoptera but there are a few sites that are useful.

For Plecoptera, Illiesia Journal has a wide range of articles on Plecoptera by experts in the field. It can be accessed here: http://www2.pms-lj.si/illiesia/html/papers.html. The only problem with the site is it doesn't seem to have a search function (or I'm missing it) so you have to scroll through a listing of articles.

For Trichoptera, the University of Minnesota has the Trichoptera Literature Database at; http://www.trichopteralit.umn.edu/.

For both plus Ephemeroptera, JSTOR has limited free access to articles. You have to register with them to gain access which can be done here: http://about.jstor.org/rr.

For Ephemeroptera there's Ephemeroptera Galactica. Only problem with it is you need to know the author of the paper you're looking for. It used to have a limited search function but after Michael Hubbard died and the site was administered by others this seems to have disappeared. The articles are here: http://www.ephemeroptera-galactica.com/mfbib.php.

And of course Google, Google Scholar and Google Books are all good scources.

How did I over look that?!


Spence - I did some editing on the captions, so if you were looking then the measurements may not have been there. Or it was brain slippage. :)
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Oldredbarn
Oldredbarn's profile picture
Novi, MI

Posts: 2600
Oldredbarn on Sep 4, 2014September 4th, 2014, 3:01 pm EDT
Spence - I did some editing on the captions, so if you were looking then the measurements may not have been there. Or it was brain slippage. :)


Brain slippage...I like that. You are so nice to this old coot! :)

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

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