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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Sweltsa (Sallfly) Stonefly Nymph Sweltsa (Sallfly) Stonefly Nymph

Dorsal view of a Sweltsa (Chloroperlidae) (Sallfly) Stonefly Nymph from the Yakima River in Washington

This species was fairly abundant in a February sample of the upper Yakima.

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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.

Hexagenia Limbata (Hex) Nymph in Captivity

This topic is about the Insect Order Ephemeroptera

Mayflies may be the most important insects for trout anglers to understand. They are an ancient order of insects, famous outside the fly-fishing world for their fragile beauty and short adult lifespan, often a single day to mate and die. The mayfly's poignant drama attracts poets and anglers alike, but anglers make the most of it.

Mayflies live more than 99% of their lives as nymphs on the river or lake bottom, filling many crucial roles in freshwater ecosystems as they feed and grow. They eventually emerge from the water as winged sub-adults called "subimagos" by scientists and "duns" by anglers. Duns evolved to be good at escaping the water, with a hydrophobic surface and hardy build, but they are clumsy fliers. Within a day or two they molt one last time into "imagos" or "spinners," the mature adults, a transformation captured in this photo series of a dun molting into a spinner. They have longer legs and tails, and sleeker, more lightweight bodies, giving them the airborne speed, agility, and long grasp they need for their midair mating rituals. They are usually darker than the duns and have shinier, more transparent wings. They die within minutes or hours after mating.

Example specimens

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Male Epeorus albertae (Pink Lady) Mayfly Spinner

Lateral view of a Male Epeorus albertae (Heptageniidae) (Pink Lady) Mayfly Spinner from the North Fork Stillaguamish River in Washington

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Male Epeorus deceptivus Mayfly Dun

Artistic view of a Male Epeorus deceptivus (Heptageniidae) Mayfly Dun from the South Fork Sauk River in Washington

The lack of a darkened humeral crossvein rules out Epeorus albertae and Epeorus dulciana. The lack of a dark macula on the forefemora rules out Epeorus longimanus. The small size rules out Epeorus grandis and Epeorus permagnus. That leaves as the only possibility known in Washington state Epeorus deceptivus. It is a small species, although not reportedly quite as small as this specimen. I couldn't find anything in the species description in Traver (1935) to definitively confirm or rule out the species ID, given that I don't have the preserved specimen to check under a microscope, but it has to be either deceptivus or something not yet reported in Washington. It was collected at the same time as a similar-sized female dun.

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Female Acentrella turbida (Tiny Blue-Winged Olive) Mayfly Spinner

Lateral view of a Female Acentrella turbida (Baetidae) (Tiny Blue-Winged Olive) Mayfly Spinner from the Middle Fork Snoqualmie River in Washington

Hdhungryman

Southern California

Posts: 2

Hdhungryman on Aug 12, 2012August 12th, 2012, 9:42 pm EDT

These hex nymphs (approximately 50-100) were collected from a private waters lake in Big Bend, Caifornia the last week in May 2012. We located them in mostly soft, shallow fine mud conditions and also within the muddy root system of the plants located in the aquarium that you see in the video. The nymphs can be clearly observed in several states of development.
Though I did not personally observe a nymph emerging from its carapace/shuck, I did notice many adult hex flying within the cabin, 2 of which I photographed and placed within this video.

The Hexagenia Limbata may be one of the most important insects for trout anglers to understand.

http://www.youtube.com/watch?v=NXjlWgWa36A&feature=youtu.be