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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.

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.
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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Big Slate Drakes

This common name refers to only one species. Click its scientific name to learn more.

Mayfly Species Hexagenia atrocaudata

These are sometimes called Big Slate Drakes.
This species is slightly smaller than Hexagenia limbata and it occurs later in the year. It is only mentioned in passing by a few authors, but it can be locally important.
Lateral view of a Female Hexagenia atrocaudata (Ephemeridae) (Late Hex) Mayfly Dun from the Teal River in Wisconsin
I found this lone Hexagenia atrocaudata dun fluttering by herself on the surface of a small, still stretch of river one evening as I paddled home from fishing for smallmouths in the warm August weather.
Male Hexagenia atrocaudata (Ephemeridae) (Late Hex) Mayfly Spinner from the Namekagon River in Wisconsin
I found this spinner and a few of his friends bobbing above the river amidst a snowstorm hatch of white Ephoron flies.

Big Slate Drakes

Scientific Name
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