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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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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

Troutnut's profile picture
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 (Very rare and somewhat outdated, but the most comprehensive book ever written about mayflies by far.)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
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's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Mar 20, 2007March 20th, 2007, 5:56 pm EDT

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

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