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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.

Ephemerella aurivillii Mayfly Nymph Pictures

This is a puzzling one to identify and I'm not sure about the species. The maxillary palp is present and segmented, and the maxillary canines are not strongly serrate laterally. I think it's Ephemerella, not Serratella. The ventral lamellae of the gills on abdominal segment 6 have a clear median notch with a depth at least half the length of the lamellae, which points toward a couple of uncommon species (most likely Ephemerella alleni), but the abdominal tubercles and coloration don't fit that species. To add to the confusion, none of the above species are expected to emerge in the fall, as far as I know. I'm going to call this one Ephemerella aurivillii for now, but that's highly uncertain.

This mayfly was collected from the Foss River in Washington on September 10th, 2020 and added to Troutnut.com by Troutnut on September 19th, 2020.

Discussions of this Nymph

Ephemerella nymph
Posted by Millcreek on Sep 24, 2020
Last reply on Sep 24, 2020 by Millcreek
I think this nymph may be Ephemerella tibialis. I am basing this on the following papers by Allen and Edmunds.



Ephemerella tibialis is in the paper on Serratella.

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