Male Trico duns hatch during the night and females hatch in the early morning before the mating swarm occurs. Photo: FFM Staff

From Pennsylvania to California and on many productive trout waters in between, the Tricorythodes hatch is the best mayfly hatch of the summer. No other hatch brings as many trout to the surface in July and August, but no other hatch leaves as many anglers scratching their heads or shaking their fists at the water in despair.

Vince Marinaro, who first wrote about the Trico hatch in his book In the Ring of the Rise, called the size 22-26 mayfly the “white-winged curse,” because it caused such selective feeding. Pennsylvania legend George Harvey made the study of Trico hatches and trout-feeding behavior a lifetime pursuit that continues today. He found that trout become so selective during the Trico spinner fall that in the early stages, they will only take imitations of the female spinner and later they feed exclusively on males. Harvey called it “the most important hatch” because if you can catch trout on Tricos, you can easily master other hatches.

The challenge of the Trico hatch continues to attract the attention of anglers looking to pass the ultimate angling test of knowledge and skill. From these anglers’ efforts, we know Harvey’s revelation is just one part of the Trico puzzle—a picture that becomes clearer and more informative as each new generation of experts tackles the Trico “problem” on their local waters.

To help you learn these new discoveries, we’ve interviewed five of the best anglers and fly tiers in the United States and share their new tactics and fly patterns that will help you catch more fish on the top Trico waters in the country. The Trico hatch will never be easy but with tutors like these, you should get top grades the next time you take the Trico test.

Identification

There are three main species that are important to North American anglers: T. minutus, which hatches across the country, and T. stygiatus and T. allectus, which are most prevalent both in the East and Midwest. T. minutus is slightly larger than the other two species but because of their similar appearance and life cycles, there is little need to distinguish one from another.

Trico duns and spinners range in size from 3.5 to 6.5 mm and can be imitated with size 18 to 26 hooks. They are the only small mayfly you are likely to encounter during the morning hours of the summer and are easily identified by the lack of a hind wing. Tricos are sometimes confused with White-winged Sulphurs from the Caenidae family, which also have no hind wing, but these insects usually inhabit warmer, slower waters and most often hatch in the late afternoon and evening.

Mike Mercer

Mike Mercer works for The Flyshop in Redding, California, and fishes the local Trico hatches on Hat Creek and the Fall River. The hatches start in mid July and end in September.

During the morning hatch of female Trico duns, the trout feed aggressively on individual insects and are much more likely to move side to side to take a fly. During the spinner fall, the insects are so thick they sometimes form mats on the surface of the water. The trout feeding lanes become so narrow that you practically have to cast your fly into an open mouth.

“It can be overwhelming for a novice angler because you see so many fish, so many bugs, and yet get no grabs,” says Mercer. “It’s very frustrating.”

Mercer says that if your casting is accurate to within inches, you can catch dozens of fish during the spinner fall. If your casting is not up to snuff, it pays to get up a little earlier and be there for the hatching female duns.

Mercer believes accuracy and presentation are the most important elements of success during a Trico hatch and uses the same fly through all phases of the hatch. Whether it’s male duns in the late evening or female spinners in the morning, he uses a parachute Trico imitation with spent Z-Lon wings and a hot orange parachute post.

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