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.

Stream photos

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Clostoeca disjuncta (Northern Caddisfly) Caddisfly Larva Clostoeca disjuncta (Northern Caddisfly) Caddisfly Larva

Lateral view of a Clostoeca disjuncta (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington

This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.

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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.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

An odd observation of Hexagenia

This topic is about the Mayfly Genus Hexagenia

These are huge mayflies. Hexagenia limbata, by far the most important species, is the second largest mayfly in the United States. The largest is its close relative, Litobrancha recurvata, which until recently was also in the genus Hexagenia.

Two minor species, Hexagenia atrocaudata and Hexagenia rigida, may be noticed later in the season than limbata.

Read each species page for emergence and other details.

Example specimens

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Female Hexagenia limbata (Hex) Mayfly Dun

This female Hex dun emerged around 11 pm, one of relatively few on the water as I rushed back to the truck to beat an approaching thunderstorm. Her tails in reality were longer than shown in the picture, but they broke off.

6
Male Hexagenia limbata (Hex) Mayfly Spinner

Artistic view of a Male Hexagenia limbata (Ephemeridae) (Hex) Mayfly Spinner from the Namekagon River in Wisconsin

13
Male Hexagenia limbata (Hex) Mayfly Spinner

Lateral view of a Male Hexagenia limbata (Ephemeridae) (Hex) Mayfly Spinner from Atkins Lake in Wisconsin

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Mar 20, 2007March 20th, 2007, 2:18 pm EDT

I'm reading up on mayfly rearing in preparation for this season, including Needham's 1935 classic "The Biology of Mayflies." (Very rare and somewhat outdated, but the most comprehensive book ever written about mayflies by far.) I found this quote strangely casual:

The eggs of Hexagenia may be obdatined from a subimago by placing her on the surface of a beaker of water and snipping off her head. She will pour them all out immediately from both oviducts -- in the case of H. occulta some 5000 of them (Needham 1908, p. 260).

I've got to wonder who first thought to try that.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681

GONZO on Mar 20, 2007March 20th, 2007, 2:53 pm EDT

If it weren't for the date, I'd guess Wes Craven! :(
No, wait...the Queen of Hearts!

Taxon

Site Editor
Plano, TX

Posts: 1311

Taxon on Mar 20, 2007March 20th, 2007, 5:56 pm EDT

Jason-

When animal dies, there is loss of muscle control, which would result in release of anything being internally retained through that device, presumably including Hexagenia eggs.

Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com