The Hex Is On

by Tim Warriner

You’ll cast a spell on the trout with these seven Hexagenia imitations.

The sun was setting when some-one from our group called “Heeeexxxx!”

Sure enough, two gigantic duns were floating down the gentle currents of the Fall River. A bat swooped down, plucked one of the insects from the water, and carted it off someplace; it reminded me of the flying monkeys snatching up Dorothy and Toto on The Wizard of Oz.

The second dun disappeared in a violent explosion of water.

I could now hear trout breaking through the surface to feed. I looked at the water and saw struggling Hexagenia limbata emergers spinning in the surface film like pinwheels. The hatch was on!

This article is about fishing the Hexagenia hatch in California, and I will share with you some flies designed to match this important mayfly. But Hexagenia are also important to Midwestern fly fishers, especially those living in the Great Lakes region, as well to anglers in New England. The principles and patterns I discuss will work wherever you encounter hatching Hexagenia and rising trout.

An Obvious Hatch
A good Hexagenia hatch feels almost prehistoric. The experience contrasts sharply with the typical mayfly hatch where an angler scratches his head squints at the water, and wonders “What are they taking?” But the Hex hatch is obvious: huge yellow bugs with upright wings float on the water and fly to the bank for safety, and the trout slash at the emergers and duns. The drama of emergence and the vulnerabilities of the mayfly are obvious even to the average angler with no entomological training.

The Hex hatch takes place at dusk. The nocturnal essence of the insect is an adaptation that protects it from the watchful eyes of most winged predators; they make such an obvious target that it is hard to imagine any would survive predation by birds and even dragonflies if they emerged in the daytime. Darkness also reduces the problem of dehydration, an issue for all mayflies, but one that is enhanced for the Hex due to the insect’s ample surface area. (To read about this and many other interesting facts concerning Hexagenia limbata, read the book, Mayflies: An Angler’s Study of Trout Water Ephemeroptera, by Malcolm Knopp and Robert Cormier.)

Darkness, however, does not provide complete protection for the vulnerable Hexagenia. I have seen Hex emergers struggle for several minutes as they attempt to crawl free of their shucks and escape the adhesion of the surface film. It takes quite a bit of time for the duns to dry their wings, and they often spasmodically flap their wings and tip over. The trout notice the disturbances on the water, and you can guess the rest—slurp.

Midwestern Hex
Midwestern hatches of Hexagenia limbata are, to say the least, more prolific than what we see in the Golden State. Perhaps due to the prevalence of Hexagenia on Michigan’s Au Sable River, one of the insect’s many nicknames is the “Michigan caddis.” There are stories of Hexagenia swarms invading Midwestern towns like locusts from the Old Testament. For the folks living near Lake Erie, the bugs are outright pests, and local residents call them “Canadian soldiers.” According to an Ohio State University research paper written by Kenneth A. Krieger, “Hexagenia emerge from the lake, often synchronously and in huge numbers, and form swarms. They are attracted to and congregate under bright lights, and decomposing piles of the insects smell fishy and serve as breeding grounds for flies.” Perhaps the smell helps explain one of their other nicknames: “fishflies.”

For Midwesterners, a strong Hexagenia hatch can pose an outright hazard. The Ohio State researcher notes that “[a]t least one south shore city . . . posted road signs in the summer of 1996 warning motorists of slippery conditions due to the ‘may fly hatch.’ In June of the same year, Hexagenia caused a brownout over much of northwestern Ohio. So many of them were attracted to the lights of a major electrical substation near the lake shore that as they settled on the equipment they conducted electricity across the insulators.” Hexagenia swarms can also become so dense that they even register on Doppler radar, and the National Oceanic and Atmospheric Administration Web site includes an article about one huge swarm titled, “Mayfly Mating Tango Captured by NWS Detroit/Pontiac Doppler Radar!” (If you’d like to see the actual radar images showing this amazing swarm of mayflies, go to

Hexagenia, like all mayflies, have no functional mouthparts, so fortunately they cannot bite. The Ohio State researcher has found, however, that while “there appears to be no direct impact on human health caused by the mayfly swarms, a few accounts refer to an allergic reaction . . . called ‘Junebug fever.’”

Here in California, the Hexagenia is a peaceful hatch, which is fine by me—sometimes there can be too much fish food on the water for the trout to notice our flies—and we refer to this insect as simply “the Hex.” Northern California’s Fall River and Lake Almanor, however, do produce reliable Hexagenia hatches.

Fall River Hex Frenzy
The Fall River is a wide, slow-moving spring creek with a soft marl bed—ideal Hexagenia habitat. The river flows through private property, and access is limited.  Wading is impossible, and all fishing is traditionally done from flat-bottomed johnboats. Typically, the Hexagenia mayflies start their emergence in late June.

The Hex hatch begins in the lower section of the river, and as the days pass, the emergence progresses upstream. Locating an area with a strong Hex hatch is essential to success, and it is best to fish the Fall River with the assistance of an experienced guide.

I divide the hatch into three stages: early, peak, and post-hatch. The early hatch period begins before sunset. During this time, you will see an occasional explosive, splashy riseform. Fish this early period intensely because it is a good time to catch a trout. The benefits of the early period are that you can easily spot your fly on the water, and your imitation does not have to compete for the trout’s attention against a thousand natural Hexagenia on the water.

When you see a rise, immediately drift a Hex emerger or dun over that spot. If the fish doesn’t take a motionless fly, twitch the fly and then let it rest again. The HexTerminator works well when fished dry during the early hatch, and if there are no takers, you can retrieve this pattern with short jerks just under the surface.

During Hex season, trout respond not only to the fly’s appearance, but also to its action in the water and the vibrations it gives off. A Hex nymph fished with a floating or intermediate-sinking line is also effective during the early hatch period.

When the sun goes down, the Hexagenia will emerge in great numbers. This is the peak hatch period. In some sections of the river, the surface will be covered with Hex duns. The Hex Appeal dun imitation is a good choice when the fish key in on this stage of the mayfly. I fish with at least two rods strung up so that I can switch from a Hex emerger to a dun without needing to tie on a new fly.

The post-hatch period is when no longer see large numbers of duns on the water and the rises become sporadic. The only light during this time is from the moon and the stars; because of the darkness, you will have to rely on sound. Cast to where you hear a trout rise, and strike with confidence when you hear the take.

Lake Almanor—Stillwater Hex Magic
Where the Fall River offers the Hexagenia experience in a spring-creek setting, Lake Almanor, in Plumas County, provides premier stillwater fishing. Lincoln Gray has fished Lake Almanor for more than 17 years and operates a stillwater fly-fishing school on the lake.  He has designed flies and developed techniques specific to meet the Hexagenia hatch. His program is comprehensive, and anglers walk away with many new skills.

I met with Lincoln in Chico, California, at Sierra Stream and Mountain, a company that includes Sierra Stream Fly Shop, Tie-Fast Tools, and Jay Fair/Eagle Fly Fishing. Lincoln is one of their managers. While I was talking with Lincoln about the Hexagenia hatch, his intensity and passion for the sport were apparent.

Lincoln does the majority of his fishing on Lake Almanor with subsurface patterns. He cautions that anglers who want to fish only top water are missing opportunities to catch trout; some knowledgeable anglers, Lincoln says, fish Hex nymphs year-round. Hexagenia nymphs molt—shed their skin—more than 30 times during the one to two years before emerging. They leave their burrows when molting and are available to the fish. Lincoln stressed that emerger and crippled Hexagenia are the most vulnerable because they “can’t fly and can’t breath underwater—a bad, bad, situation.”

Lake Almanor is known for its large trout as well as smallmouth bass. At times, however, anglers face the challenge of locating fish.

Lincoln explained that while many areas in the lake have strong Hexagenia hatches, they are often too shallow for the trout, which must migrate in search of cool water. Successful anglers fish near inlets and springs, and using a float tube or pontoon boat is the most affective means for fishing Lake Almanor. Underwater structures such as shoals and drop-offs are also productive areas.

For an evening’s fishing, Lincoln straps six rods onto his pontoon boat: two rods with intermediate lines, two with sinking-tip lines, one with a floating line, and another with a type-III sinking line. Having several 5- or 6-weight rods ready to go allows him to adapt quickly to changes in the lake environment and fish behavior. The rods also help eliminate the need to tie on flies in the dark, which is always a consideration when fishing the Hex hatch.

Anglers fish sinking lines using a variety of retrieves. Lincoln says most new stillwater anglers retrieve the fly too fast, and advises to “use a slow re- trieve.” He demonstrated for me how to occasionally punctuate the slow retrieve with a series of faster strips, giving the appearance of an insect accelerating to the surface for emergence.

Lincoln’s Hexagenia imitations are the result of a team design effort with his identical twin brother, Lance. When developing a new pattern, Lincoln ties a “rough” fly or makes a sketch of his idea, and Lance, who has been a professional tier since age 13, produces several prototypes. Lincoln then fishes with the flies and makes modifications based upon their performance.

Gray’s Stillborn Hex, Gray’s Hex Nymph, Gray’s TS Bugger, Gray’s Hex Emerger, and Gray’s Hex Dun are Lincoln’s go-to flies during Hex season. Lincoln is most passionate about the TS Bugger. He explains that gold/yellow and brown/olive are “Hex colors.” Lincoln ties the thorax of the TS Bugger using Jay Fair Long Shuck and the abdomen with Short Shuck. Using these materials, which come in different lengths, gives the fly “shoulders.” Lincoln often fishes the TS Bugger in tandem with Gray’s Hex Nymph; he places the TS Bugger about 12 to 15 inches below the nymph.

Lincoln fishes Gray’s Hex Emerger like a dry fly, and often trails a Gray’s Hex Stillborn 6 to 8 inches below the emerger. He casts these flies ahead of a cruising, surface-feeding trout. Lincoln teaches anglers to make a subtle twitch immediately after the flies land on the surface. He shares my observation that during a Hex hatch, twitching or stripping a fly imitates a struggling insect and frequently draws strikes.

Fishing the Hex hatch is not about the number of fish you catch. Witnessing the emergence of the gargantuan Hexagenia mayfly is itself memorable, and the best memories will be the explosive surface strikes to your dry flies and the arm-wrenching pulls when the trout snatch your subsurface offerings. If you have not yet experienced the spectacle of a Hexagenia hatch, perhaps it is time you get Hexed!

Tim Warriner is a talented angler and fly tier who lives in California. This is his first appearance in our magazine.

Tag it:
Furl it!