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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 Epeorus albertae (Heptageniidae) (Pink Lady) Mayfly Nymph from the East Fork Issaquah Creek in Washington
This specimen keys to the Epeorus albertae group of species. Of the five species in that group, the two known in Washington state are Epeorus albertae and Epeorus dulciana. Of the two, albertae has been collected in vastly more locations in Washington than dulciana, suggesting it is far more common. On that basis alone I'm tentatively putting this nymph in albertae, with the large caveat that there's no real information to rule out dulciana.
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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Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
Some notes from identifying this specimen under the microscope:

1. The hind wing has three longitudinal veins, but the third is faint, short (about half the length of the wing), and close to the wing margin.
2. Then antenna is brown fading into white at the tip, and the base is ringed with white.
3. The joints of the tarsal segments on the middle and hind leg have fine black markings.

It was also collected in association with a female spinner.
Troutnut
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Bellevue, WA

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Troutnut on Nov 6, 2020November 6th, 2020, 3:16 pm EST
Does anyone here know any decent resources for identifying adult Baetis? I haven't found much.

This specimen sure seems to nicely fit the original description of Baetis alius adults. But I can't find very precise descriptions (let alone a key) for flavistriga and tricaudatus, both of which are other likely options given the location.

These made for a good fishable hatch on Silver Creek, so it sure would be nice to know what they are.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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