Each May, predictable mayfly hatches explode across Maine’s bottom third, and in the subimago stage, the bugs float on the surface and bring salmonids topside, extremely visible rises that excite fly rodders.

 This column has occasionally mentioned a basic tactic that helps folks catch trout, salmon and even bass during insect emergences. Fly fishers match a fly in size, color and silhouette to the prevalent insect on or in the water.

This advice also works for imitating baitfish with streamers or bucktails. Game fish may chase schools of baitfish, so wise anglers imitate the swimming forage with a fly (or lure) that looks like the natural.

Hatch matching can rise to a more complex level. Fly fishers determine the insect’s species or at least genus, particularly if a bug hatches for a long enough time — say each afternoon for 10 to 14 days or better yet longer. Prolonged breeding activity makes the research worthwhile.

For instance, a popular mayfly with the Latin name Ephemerella subvaria emerges on May afternoons in southern and central Maine, and in colder climates of the north country, the same hatch may not kick off until early June. We colloquially call this insect “red quill” or “Hendrickson,” and it comes off in rivers and large streams for two weeks. The exact beginning and end depend on latitude, elevation and weather. Myriad fly rodders key on this hatch with size 12 or 14 Red Quill, Hendrickson or Compara-dun dry flies or Hendrickson nymphs.

When perspicacious fly fishers match hatches, they use entomology books such as Caucci and Nastasi’s “Hatches” or Knopp and Cormier’s “Mayflies” to identify the insect. They then read up on how the species behaves in the nymph stage before the hatch and in the dun phase as they’re hatching. Then, folks duplicate the movement of their imitation to the natural motion of the bugs.

This doesn’t require a scientist’s mind, either. When fly rodders speak generically about mayflies, they often put them into four categories: 1. Crawlers, 2. clingers, 3. swimmers and 4. burrowers. This tells us plenty about how to fish our nymph and dun imitations.

Let’s say the bug in question is our old friend the red quill or Hendrickson, a member of the crawler family. Crawler and clinger mayflies spend their life on bottom, crawling around or clinging to submerged wood and rocks. When they become active an hour or so before a hatch, the current washes many off bottom, and they drift downstream, vulnerable to foraging fish. As the bugs fight to get back on bottom and safety, salmonids feed on them voraciously.

Fly rodders armed with that knowledge let their nymphs float along naturally on a dead-drift just like the natural. Often, they use a weighted fly to get near bottom where the dislodged insects usually drift with the current.

Immediately after hatching, lots of mayflies in the dun stage float on the surface film to dry their wings before flying, and success depends on the dry-fly imitation floating at the exact same speed as the current.

Early blue-winged olives (BWOs) often belong to the crawler family, but by summer, many of the hatching BWOs are members of the swimmer family and run smaller — size 20 to 24. A dead-drift presentation works poorly for swimming nymphs.

When matching swimming nymphs, astute fly fishers cast imitations such as an appropriately sized Pheasant Tail quartering across and downstream, and then they allow the fly to swing in a tight arc. Next they inch the PT back like an insect fighting the current — a tactic as old as fly fishing.

(Mayflies in the nymph or dun stage instinctively swim or fly upstream. If aquatic bugs didn’t fight currents, flowing waters would eventually wash them out of rivers into lakes, ponds and ocean below.)

One popular Maine mayfly hatches from mid-June through July, depending on latitude, elevation and weather. We call it “Hex” after its Latin name Hexagenia limbata. Fly fishers who know entomology match this huge bug with a size 6 Compara-dun Hex or Hex Wiggle Nymph.

Hex larvae burrow in bottom silt in rivers, ponds and lakes until ready to hatch. Then they swim to the surface and often emerge from the nymphal shuck while floating on the meniscus. A Hex nymph imitating a natural that is swimming up from bottom often works far better than a dry fly.

In states like Michigan, Hexes are an important river hatch, but here in Maine, this species occurs more in ponds and lakes, a huge mouthful that brings wall-hanger salmonids to the surface.

These insects mentioned above are a small sampling of what fly rodders often take upon themselves to learn in order to catch more fish. The key to success begins with identifying them and then reading up on their behavioral patterns — a perfect example of experience and scholarship.

Soon in this column, I’ll talk about matching caddises. With a few tips, folks can do well with this insect family that’s so prevalent in Maine.

Ken Allen of Belgrade Lakes is a writer, editor and photographer. He can be contacted at: [email protected]