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.

A beautiful braided reach of the Sag River, with the Philip Smith Mountains in the Arctic National Wildlife Refuge (ANWR) in the background.

From the Sagavanirktok River in Alaska

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

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.

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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.

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Hex Hatch 2012

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.

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Male Hexagenia limbata (Hex) Mayfly Spinner

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

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Male Hexagenia limbata (Hex) Mayfly Spinner

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

Hdhungryman

Southern California

Posts: 2

Hdhungryman on Apr 15, 2012April 15th, 2012, 4:57 pm EDT

Forget the end of the world. The Hex Hatch is just about on again. For more than 7 years now, I have been making the journey north and have encountered one of the most prolific hex hatches I have ever seen (in the West that is). We all know that there are very specific conditions that must exist in order for this amazing event to occur. There are a few notable locations though I have found Henderson Springs in Big Bend, CA to be the most exciting from the perspective of a flyfisherman.

I am constantly keeping an eye out for when the hatch starts in this region. I will do my best to keep my post current as I get further updates. Make it a great season!

PaulRoberts

Colorado

Posts: 1776

PaulRoberts on Apr 15, 2012April 15th, 2012, 5:09 pm EDT

Good luck, man!

Entoman

Northern CA & ID

Posts: 2604

Entoman on Apr 15, 2012April 15th, 2012, 7:45 pm EDT

Welcome to the forum Hungryman.

Been there many times. Catch any big catfish? It's bizarre how the springs allow both them and trout to inhabit the same water. Caught one that tipped the scales at over 12 lb.'s and was afraid it was going to sink my float tube with one of it's spines! (I wonder if that's a record for catfish on a dry fly?) :)

"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman

Crepuscular

Boiling Springs, PA

Posts: 920

Crepuscular on Apr 16, 2012April 16th, 2012, 4:30 am EDT

Caught one that tipped the scales at over 12 lb.'s and was afraid it was going to sink my float tube with one of it's spines! (I wonder if that's a record for catfish on a dry fly?) :)

I don't know but during the Ephoron leukon hatch on the Susquehanna river it is not unusual to catch enormous channel cats! It's very challenging to get the fly directly on the nose of those cats when they are feeding on the spinners. But man do they pull! I've caught and seen friends catch them that go at least that big!

THETHUMB

Posts: 1

THETHUMB on Jun 3, 2012June 3rd, 2012, 1:39 pm EDT

This last week was a perfect condition for the Henderson Hex Hatch. Although I missed it, several friends were there with fantastic stories and results.

Taxon