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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 Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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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Ephemerella aurivillii Mayfly Nymph Pictures

Artistic view of a Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska
Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska
Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska
Dorsal view of a Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska
Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska
Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska
Ruler view of a Ephemerella aurivillii (Ephemerellidae) Mayfly Nymph from the Chena River in Alaska The smallest ruler marks are 1 mm.

This mayfly was collected from the Chena River in Alaska on May 10th, 2008 and added to Troutnut.com by Troutnut on April 20th, 2011.

Discussions of this Nymph

E. aurivillii
1 replies
Posted by Entoman on Apr 26, 2011
Last reply on Apr 26, 2011 by Troutnut
Jason,

I was going to share my belief that this specimen is E. aurivillii, but I see you beat me to it.:) Oh well, with all the "fast gun" Bugmeisters on this site, there are really only two types, "the quick and the dead!":)

This species is fairly common in the West, but nobody seems to know what the duns look like. If you could catch some ripe nymphs this spring and hatch them into duns, it would be excellent reportage.

Regards,

Kurt

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References

Ephemerella aurivillii Mayfly Nymph Pictures

Collection details
Location: Chena River, Alaska
Date: May 10th, 2008
Added to site: April 20th, 2011
Author: Troutnut
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