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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 Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
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 Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from the Bois Brule River in Wisconsin
I'm guessing this specimen is in the genus Acerpenna because of the very sharp costal process on her hind wing. I'm guessing pygmaea because it is the most common species.

Editor note: Not Acerpenna. This is most likely Baetis. See comments on this male specimen for rationale. Also compare with the female specimen associated with it.
Taxon
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Taxon on Jul 1, 2006July 1st, 2006, 6:54 pm EDT
Jason-

My guess would be Baetis brunneicolor.

Roger
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Troutnut
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Troutnut on Jul 2, 2006July 2nd, 2006, 3:20 am EDT
How come?
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Taxon
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Taxon on Jul 6, 2006July 6th, 2006, 6:45 am EDT
Jason-

Oh, sorry. Just discovered your response. Because of the striking similarity of your specimen's fore wing venation to the that of Baetis brunneicolor portrayed in Leonard & Leonard, page 87, Fig. 51.

Here is your photo arranged for comparison purposes:


Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
Troutnut
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Troutnut on Jul 6, 2006July 6th, 2006, 7:25 am EDT
Ok, thanks. I just looked at Leonard and you're right that the venation is strikingly similar (though not identical). They don't have very many other Baetis wings to compare to, though, so I'm hesitant to rule out the other species on those grounds.

The costal process on the hind wing is much sharper in this specimen than in the Leondards' drawing. I think that's a fairly important characteristic for this family and it's one reason I'm hesitant to call it Baetis.

Also, the Leonards show some intercalary veins on the hind wings of brunneicolor, which I don't see in this photo. That could be due to individual variation or bad focus in the photo, though.

The taxonomy of this whole family is such a mess right now. I really hope somebody publishes a definitive key to the genera soon based on something better than mandible setae and the like.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
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Troutnut on Sep 21, 2006September 21st, 2006, 5:28 pm EDT
I'm even more confident that this is Acerpenna now that I've photographed an extremely similar specimen from upstate NY. The new female was associated with a male which I also photographed, and it keyed fairly confidently to Acerpenna in Merritt & Cummins.

I've fallen a bit behind on posting new pictures I've taken. I've got about 30 new specimens to put up, I think, including the Acerpenna pair. All that's coming ASAP.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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