One of the most important fly hatches of the year is about to begin and in some of the southern areas the hatch may be started. The Hexagenia limbata, the largest of the many species of mayflies will bring out the largest and most wary trout and salmon as well as other species that feed on insects and provides some of the most exciting fly fishing of the season.

Most fishermen refer to these huge mayflies as “Hex’’ or “Hex flies’’ but there are also confused with the hatch of another large mayfly, the green drake. But it doesn’t make much difference in the naming or the proper identification, as they both are so close in habits and their great attraction to fish. The important thing is to be there when they are.

Normally Hex flies are associated with back-country fishing waters, but not always. But the clean and more healthy waters of the North Country seems to supply the best fishing when the Hex hatch is on and usually is timed to almost the same week each year. In New England’s North Country, the hatch should be on as you read this, or at least in its infancy.

Most of the fly fishing is just at dusk when the big flies start to emerge and the hatch gets going faster and faster and continues into the night. In a lot of areas where there is a limit on hour of fishing that doesn’t mean that you will loose out on some great fishing. During the pre-hatch period that actually starts as soon as the sun hits the water in the morning, these insects will start to move and get ready to shed their nymphal cases.

Fly fishermen who are on to this fact can have some great nymph and wet fly fishing by using patterns that mimic this activity. The Hex fly nymphs are usually a muted yellow or even light gray with a hint of yellow. They are easily imitated with a lightly hackled muddler style wet fly that is anywhere from a half inch to an inch long. To mimic the unique swimming action of the Hex nymph some of the more imaginative fly tiers will use two body sections joined by a loose connection that allows the nymph, when retrieved, to produce a lifelike wiggling effect.

While most fly anglers use the cast and a rather quick and jerky retrieve just under the water surface when using Hex nymphs, trolling with a sink tip fly line and imparting some action to the fly also is surprisingly effective. Flies such as the green drake wet fly and the maple syrup are quite popular in the northcountry but also a dull yellow marabou streamer in size 8, 10 or 12 can also provide a lot of hits while trolling or casting. Imparting action to the fly is very important!

For fishing the night hatch, it’s hard to say how exact imitation of the mature insect is important. Since a lot of trout action is eating the nymphal stager of the fly as it emerges, which actually looks like just a small lump of wiggling hair, the feeding fish will often hit a fly that has no resemblance of anything in nature. We’ve seen fish caught during the Hex hatch on simple ties that are only a black body and single upright wing and skimpy tail, all tied with the same synthetic yarn. And the same time, we’ve seen fish after fish pass up a museum quality dry fly that you’d swear was the real thing.

Two schools of thought seem to bring about the same results. Some dry fly fishermen believe in the stealth approach and just let their fly sit on the water with no movement while others twitch their fly in a very slow retrieve. But we’ve also been out on the water fishing the hatch when a huge brook trout was taken by an angler that didn’t have a cue and was trolling a big bushy dry fly that made a wake like a small water skier.

Fishing this hatch can be the most rewarding or the most frustrating event of your fishing season but if you don’t go you won’t have either of those memories. Our choice is to go and either give those fish a real beating or come back with out tail between out legs.

Dick Pinney’s Guidelines column appears weekly in the New Hampshire Sunday News. Email him at DoDuckInn@aol.com.