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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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Dorsal view of a Gomphidae Dragonfly Nymph from the Namekagon River in Wisconsin
Waxsmith
CANADA

Posts: 6
Waxsmith on Feb 11, 2011February 11th, 2011, 2:26 pm EST
I do know these nymphs are biggies alright, but just what is the average size of them, like their length in "mm"?
What is this supposed to look like, example please.
Taxon
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Feb 11, 2011February 11th, 2011, 4:33 pm EST
A.K.-

According to McCafferty, Gomphid (Clubtail) nymphs generally measure from 23-40 mm. (and rarely as long as 65 mm.) at maturity.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com

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