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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 Limnephilidae (Giant Sedges) Caddisfly Larva from the Yakima River in Washington
This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
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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Black and Olive Duns

Like most common names,"Black and Olive Dun" can refer to more than one taxon. They're previewed below, along with 2 specimens. For more detail click through to the scientific names.

Mayfly Species Leptophlebia johnsoni

These are sometimes called Black and Olive Duns.

Mayfly Species Hexagenia atrocaudata

These are very rarely called Black and Olive Duns.
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.

Black and Olive Duns

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