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By KEN ALLEN 07/05/2008

Each summer, a huge mayfly brings Maine’s trophy trout and salmon to the surface, and it’s occurring right now in large sections of the state, thrilling fly rodders who love this evening hatch. Myriad anglers live for this annual event just as other folks look forward to deer season.
The mayfly goes by the scientific designation Hexagenia limbata, but
in Maine, most folks refer to it colloquially as “Hex” or “green drake.” … More on the appropriate name later.
Whatever anyone calls this aquatic, mud-burrowing bug, though, it grows huge by insect standards. The body of a newly emerged dun measures 2 1/2 to 2 3/4 inches long, including the tail. They look like mini-sailboats with scalene sails as they sit on the surface to dry their upright wings before flying off. Salmonids and even bass and perch gorge on the duns and emerging nymphs.
As a general rule, Midwestern Hexes in the dun stage have a decidedly more olive cast than they do in Maine. In this state, the body and heavily veined wings are often quite yellowish with a subtle olive cast. The degree of yellow or olive depends on the water, though, according to renowned New Hampshire entomologist, Tom Ames. This author of Hatch Guide to New England Streams once told me that Hexes may range from bright yellow to reddish brown.
Despite the overall color of this insect, the abdomen’s back has purplish-brown markings that look (sort of) diamond shaped. The six legs and two tails have the same shade as the abdomen and purplish-brown spots.
When Hexes emerge in a particular water, the hatch may continue for 10 to 14 days, but that varies with natural conditions such as water temperature, which is related to how high air thermometers soar.
For example, drought conditions over several days can end the hatch in a hurry because of rapidly rising water temps, but relatively mild, cool weather can keep it going for three weeks — or longer.
Depending on latitude, elevation and weather, Hexes emerge from silt-bottomed lakes, ponds or rivers from mid-June in southern Maine to early and even mid-August in northern Aroostook County. Apparently, it’s a little late this year, but that depends on the location.
Most fly rodders associate this hatch with dusk and certainly after dark, but I’ve seen Hexes hatch sporadically all afternoon on lowery, cool days. When that happens, life in Maine is the way it should be.
During the Hex hatch, savvy fly rodder cover rises with a dry fly or nymph that matches the natural in size, color and silhouette. I like to drop a dry on a rise ring or in front of the direction a trout or salmon is moving, easy to determine when a single fish takes one insect after another. With a nymph, I cast it to one side of the rise ring and work it back where I think the fish is watching. With that plan, action can be blistering.
My introduction to this insect came at the tender age of 14 when a magazine article caught my eye. The writer was talking about a hatch in the Midwest and called it a “Michigan caddis.” He did explain that it wasn’t a caddis but actually a mayfly, which in those days meant nothing to me.
The author said motels and hotels near silt-bottomed, cold-water rivers where the bug hatched filled a year in advance because folks would book a room or tent site 12 months ahead to assure themselves of lodging.
That last point wowed me — an insect spurring the Midwest economy. These days, though, fly-fishing’s popularity has stimulated tourism worldwide as traveling anglers flock to specific hatches.
When Fly Fisherman Magazine first started, Don Zahner, the editor, published an article on the Michigan caddis, in which the author explained it was a mayfly and furnished the scientific name Hexagenia limbata.
Like the magazine piece years before, the article highlighted the hatch as a river event. In Maine, though, we associate Hexes with lakes and ponds far more than rivers, although silt-bottomed pools in the Sheepscot River bottomland between Sheepscot Pond and Route 105 has Hex hatches on mid to late June evening.
(Along that line, we normally associate March browns [Stenonema vicarium] as creatures of riparian habitat. However, Ames once told me that true March browns hatch in selected Maine ponds.)
My first direct experience with Hexes occurred in 1972 on Frost Pond northwest of Ripogenus Dam, and it really excited me. I was casting a size 10 Flick March Brown to rising brookies, some 2-pounders, and the fly worked well enough. Size 10 was too small to produce consistently, though.
Three years later, I tied up a bunch of Hex Compara-duns on size 6, 2x long hooks and Hex wiggle nymphs on two, size 10 hooks with the hook cut off one of the hooks after the tying, leaving just the shank. (I hooked the two flies together with a loop of .013 monofilament during the tying.) These wiggle nymphs work superbly during the hatch when I sunk them to the bottom and then retrieved them to the surface a la an emerging nymph.
Which brings up a point. When folks talk about blue-winged olive (BWO) or sulfur-dun hatches, they routinely grab a BWO or Sulfur Dun dry fly or nymph to match and go at it. It’s the same with March-brown or red-quill hatches. With Hexes, though, folks often ask, “What works in a Hex hatch — a Grizzly Wulff, Hornberg or what?”
Anything works at times, but fly rodders do better when they match the imitation to the natural insect (or baitfish) in size, color and silhouette. So, knowing that, why not use flies designed to match the specific Hex hatch? I love the Hex Compara-dun and Hex wiggle nymph.
Some fly rodders refer to Hexes as “green drakes,” although guides, fly-shop owners, writers, etc. are educating them to the proper designation.
The sole big deal about misnaming the bug strikes anglers with entomological knowledge as obvious. A true green drake (Ephemera guttlulata) is a different size and color than a Hex, so if you tell a fly fisher – say from Pennsylvania or even Portland – that he or she should bring Green Drake dry flies to a Hex hatch, the chosen pattern will be smaller and much greener than a Hex imitation. Because trout can be extremely picky in the Hex hatch, that mistake can lead to a long, boring evening.
Just for the record, I’ve never seen a true green drake in Maine, a species that requires alkaline water as opposed to this state’s typically acidic water. Entomologists claim we do have them in selected places, though.

Ken Allen, of Belgrade Lakes, is a writer, editor and photographer.

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