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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.

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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Great Lead-Winged Drakes

Like most common names,"Great Lead-Winged Drake" can refer to more than one taxon. They're previewed below, along with 5 specimens. For more detail click through to the scientific names.

Mayfly Species Hexagenia limbata

These are sometimes called Great Lead-Winged Drakes.
It starts like a rise of small trout. There are dimples on the surface--fingerling trout eating midges, perhaps. But these are no fish. The water breaks and out pop the yellow sails of a giant Hexagenia dun. Then another. And another. A vortex appears in a flash below the mayfly and it vanishes with a slurp so loud it echoes off the distant bank. A square tail like a shark fin breaks the surface behind the swirl as a brown trout twice the size of your net retreats back to his deeper lair. The Hex hatch is on.

This Midwestern legend plays out every year on calm, dark, humid nights in early July. Anglers who only fly fish once a year drive hundreds of miles to play their part in the drama, while the mayflies themselves make the television news by showing up on doppler radar or calling snowplows out of dormancy to remove layers of Hexagenia (or "Hex") duns from the bridges. In the cold trout rivers of Wisconsin and Michigan, huge nocturnal brown trout whose usual menu consists of smaller brown trout become, for a week or so, prime dry fly quarry.

According to the literature, these are the second largest mayflies in the United States, behind the related Litobrancha recurvata flies. However, there are reports of limbata exceeding 40mm in some locales, which would make them the largest.
Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the White River in Wisconsin
Lateral view of a Male Hexagenia limbata (Ephemeridae) (Hex) Mayfly Spinner from Atkins Lake in Wisconsin
Hexagenia limbata (Ephemeridae) (Hex) Mayfly Nymph from unknown in Wisconsin

Mayfly Species Hexagenia atrocaudata

These are very rarely called Great Lead-Winged 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.

Great Lead-Winged Drakes

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