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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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Dryfly has attached this picture to aid in identification. The message is below.
Dryfly
rochester mn

Posts: 133
Dryfly on Mar 18, 2007March 18th, 2007, 7:39 am EDT
caught in riffle about 2 cm long any ideas on what genus it might be
Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on Mar 18, 2007March 18th, 2007, 11:15 am EDT
Dryfly-

It appears that the larval case is flattened on the bottom, as opposed to being cylindrical. Is that true? It also appears that the case is made entirely of plant material, as opposed having rock particles incorporated in its construction. Is that true?
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Dryfly
rochester mn

Posts: 133
Dryfly on Mar 18, 2007March 18th, 2007, 11:32 am EDT
taxon
it is under water so that is why it appears to be flat.
it is cylindrical

the case it made primarily with fine pieces of rock with some sticks toward the back
this may help I collected it in se minnesota

GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Mar 18, 2007March 18th, 2007, 12:23 pm EDT
Roger, I was also deceived by the optical illusion caused by the water.

Dryfly, if you could extract the larva from the case without damage and rephotograph it, the identification should be easier. Perhaps Roger, Konchu, or David would then be better equipped to nail it down with the additional information that would be provided.
Taxon
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Site Editor
Plano, TX

Posts: 1311
Taxon on Mar 18, 2007March 18th, 2007, 1:50 pm EDT
Dryfly-

The only family of caddisflies (of which I am aware), which builds stout, cylindrical, not gradually tapered or curved cases, made mainly or entirely of rock fragments, and would also be as large as your specimen is Limnephilidae.

The following Limnephilidae species reside in Minnesota:

Frenesia missa
Limnephilus indivisus
Limnephilus sericeus
Limnephilus submonilifer
Pycnopsyche guttifera
Pycnopsyche lepida
Pycnopsyche scabripennis
Platycentropus radiatus
Onocosmoecus unicolor
Hesperophylax designatus
Hydatophylax argus


Of those, only Fresnia missa (Dot-Winged Sedge), and Hesperophylax designatus (Silver Stripe Sedge) build cases resembling those of your specimen. Fresnia missa only reaches a length of 13.5 mm, whereas Hesperophylax designatus reaches a length of 20 mm., so that’s what my guess would be.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Mar 18, 2007March 18th, 2007, 3:57 pm EDT
Really nice deductive reasoning, Roger!
Taxon
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Plano, TX

Posts: 1311
Taxon on Mar 18, 2007March 18th, 2007, 4:57 pm EDT
Really nice deductive reasoning, Roger!

Thanks, Gonzo. However, there is (at least) one caddisfly specialist who frequents this site, so I'm kind of waiting for "the other foot" to fall!
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Mar 18, 2007March 18th, 2007, 5:26 pm EDT
I know what you mean, Roger, but I still think it was an impressive application of both logic and resources. :)
Dryfly
rochester mn

Posts: 133
Dryfly on Mar 19, 2007March 19th, 2007, 12:08 am EDT
thanks taxon and gonzo for your quick replies
I appreciate it
i'll post pics of the larva out of the case later today

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