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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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Cinygmula (Dark Red Quill) Mayfly Nymph Pictures

This very strange nymph appears to be undoubtedly Cinygmula, yet it lacks the telltale protruding mouthparts that usually make that genus so easy to identify.

Ruler view of a Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska The smallest ruler marks are 1 mm.
Ventral view of a Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska
Dorsal view of a Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska
Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska
Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska
Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska
Cinygmula (Heptageniidae) (Dark Red Quill) Mayfly Nymph from the Gulkana River in Alaska

This mayfly was collected from the Gulkana River in Alaska on July 17th, 2011 and added to Troutnut.com by Troutnut on July 20th, 2011.

Discussions of this Nymph

A Cinygmula nymph without protruding mouthparts?
12 replies
Posted by Troutnut on Jul 20, 2011
Last reply on Mar 28, 2013 by Brookyman
I've never heard of such a thing, yet here it is, unless I'm badly mistaken. The gills and all the other features scream Cinygmula, as does the fact that it was collected with hundreds of other Cinygmula nymphs representing (I think) at least two species.

Anyone know what's going on with the mouth?

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References

Cinygmula (Dark Red Quill) Mayfly Nymph Pictures

Collection details
Location: Gulkana River, Alaska
Date: July 17th, 2011
Added to site: July 20th, 2011
Author: Troutnut
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