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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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Epeorus vitreus (Sulphur) Mayfly Nymph Pictures

Key features I discerned with a microscope include that the femoral flange is blunt (later note: on nymphs of this size, it's somewhat ambiguous and the femora can be damaged in the collection process), the postero-lateral spines have a longer anterior, the first gill is not extended, all gills are tracheated, and the femora have a distinctive brown spot on the center while all the other spots are gray.

This mayfly was collected from unknown in Wisconsin on February 7th, 2004 and added to Troutnut.com by Troutnut on January 25th, 2006.


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Epeorus vitreus (Sulphur) Mayfly Nymph Pictures

Collection details
Location: unknown, Wisconsin
Date: February 7th, 2004
Added to site: January 25th, 2006
Author: Troutnut
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