It's possible to catch trophy squaretails during the Hex Mayfly hatch. Credit: Courtesy of Maine Department of Inland Fisheries and Wildlife

June and July’s strawberry season is eagerly awaited by us shortcake lovers. At the same time of year, many of us fly anglers also look forward to another

“season” — the Hex hatch, or as many Mainers call it, the Green Drake hatch.

This long-awaited hatch is generated by a huge mayfly that scientists named

Hexagenia limbata. It belongs to a group of mayflies in which the nymphs burrow

into the bottom sediment of many Maine lakes and ponds. After two years of

living benthically, the almost 2-inch nymphs swim to the surface hatching into

elegant Hex mayflies called duns.

The females are about 2 inches long, counting the two tails and body, while the males are a bit shorter. Both sexes are colored with shades of yellows and tans. Sorry folks, no green on this species.

Confusion reigns supreme with some mayflies since fly fishers also use the word

“green” to name several other species of a similar size. One of those, the Eastern

Green Drake (Ephemera guttulata) is also commonly called a Green Drake, but it

is not the same critter.

The sure-fire way to tell the difference is to count the number of tails: adult Hex mayflies have only two tails, whereas the Eastern Green Drake has three tails. (Mayfly photos are often mislabeled on the internet).

Compounding the problem is that both species often overlap at the same time of

year when hatching, although Maine has very few waters that harbor the

limestone-loving, three-tailed Eastern Green Drakes.

Why get so excited about the Hexagenia (Green Drake) Hatch? It’s because these

super-sized mayflies offer a pretty darn good package of protein, and that brings

super-sized fish to the surface like a magnet. And that means fly fishers have a

chance to land trophy trout on a dry fly. In my mind, it rarely gets better than

that. I call it Hexitis.

Adult Hex mayflies only live for about two days, and during that time, the Hex

duns transform into their last phase, called a spinner. The male and female

spinners mate in a ritual flight, followed by the females depositing their eggs into

the water, and then both adults die. The life cycle continues as the eggs hatch

into nymphs that tunnel into the bottom silt and mud.

When can fly anglers expect to see Hex mayflies? Reports from the Greenville

area indicate the hatch has already started on local ponds, showing up during the

week of June 20. Hex hatches on small, shallow ponds occur first, with deep

lakes and high elevation waters happening a little later.

In past years, the last week in June and the first week in July were always good bets but, more recently, the tendency has been for this hatch to commence earlier in the year. I believe it’s because of that bugaboo — climate change.

The two most important factors that determine hatch onset and hatch length (in

days) is the ambient air temperature, which then determines water temperature.
Several days with significantly high temperatures (80-90 degrees Fahrenheit) usually means an earlier starting hatch, whereas cold, rainy weather tends to delay it.

Blast furnace heat during the hatch usually brings it to a short ending, a week or less, but more typically it lasts 10 days to two weeks. I have found that most Hex hatches begin when surface temperatures are between 65-70 degrees.

Hexagenia mayflies are eaten by all kinds of fish, in both the nymphal and adult

stages, but in Maine, the fish species most often targeted by fly anglers is the

squaretail trout.

There is a downside to fly fishing this hallowed hatch. The majority of Hex

mayflies come off the water near dark, and the amount of time to land fish when

they are rising is short, maybe 15 to 30 minutes if you are lucky. As a result, an

angler needs to be fully prepared and should not waste time during the hatch

tying on new flies or untangling fly lines and rods. If using a canoe, I recommend

taking two fly rods that are all ready to use. When I fish from a boat, I take three

fly rods all rigged for action. Time is of the essence during this hatch!

Using dry flies is the classic way to fish for salmonids during a Hex Hatch, but I

don’t always find them to be that fussy. Every Hex angler has a favorite fly, but

the truth is, many different flies catch fish during this hatch. A few favorites

are Wulffs, Comparaduns, Hex Dry Flies, Hex Emergers, Hex Rubber Legs and

Stimulators. Hex Nymphs can also fool trout both before and during a hatch, using

either a sinking line or floating line on a 9 1/2-foot fly rod.

While fishing this hatch, be sure to lead cruising fish when casting, check the fly

every so often for tangles, and if you have the patience, cast and wait … and

wait … for the fish to come to you. It does work. Also, take plenty of bug dope and

don’t bother with the Solunar Table.

Maine has hundreds of waters that support the Hex Hatch. A few are Sourdnahunk

Lake, Pierce Pond, the Deboullie Region and the majority of Baxter State Park’s

ponds. There are also many fine sporting camps that cater to Hex Hatch fly

anglers including Bradford Camps, Red River Camps, Nahmakanta Lake

Wilderness Camps, Cobb’s Pierce Pond Camps and Grant’s Kennebago Camps.

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Leighton Wass, Outdoors contributor

Leighton Wass grew up in Southwest Harbor and graduated from Norwich University with a B.S. in science education. He taught high school biology in Vermont for 33 years and also is a freelance writer. At...