Other Common Names: White-winged curse
Scientific Name: genus Tricorythodes

Tricos are tiny mayflies of the crawler type. They have dark-hued bodies and white wings. Nymphs are not important, but hatches and spinner falls can trigger aggressive, selective feeding by trout.

Nymphs live almost anywhere there is moving water, but they favor slow currents where a little silt has settled over the bottom. The hatch season gets rolling in July, ramps up until August, then stays strong until the first frosts of October. One reason for the long hatch season is that tricos have two-broods in the summer.

Nymphs are unimportant to anglers, but duns and spinners are major events. Female duns hatch early in the morning and molt to spinners within minutes. Male duns hatch in late evening or dark. As the morning hatch fades, spinners return to the water. The males fall first, and the females a brief time later.

It's important to recognize this sequence of male hatch, male spinner fall, female spinner fall because the males and females are different sizes and colors, and trout can be extremely selective about these bugs because there are so many of them on the water at one time.

This insect's nickname, "the white-winged curse," should serve as a warning. Trout can be maddeningly fussy about tricos, and everything that contributes to angling success is contradicted by harsh realities: imitations should ride as high in the water as possible, but without much hackle; tippets need to be 7X and long, but casts should be accurate and the leader needs to lie out straight; downstream presentations work best, but the wind is usually blowing upstream.


How to Match a Trico

Hatches are matched from Westfly's database of "standard" fly patterns.

Size 18-22 Hairwing Dun, Sparkle Dun. black body, clear wing, or dark brown/white wing
Slow runs, lakes: standard dry fly, chuck-and-sit
Size 18-22 Rusty Spinner. black body, clear wing, or dark brown/white wing
Slow runs, lakes: standard dry fly, chuck-and-sit


NYMPH COLOR: dark brown

DUN SIZE: 3-6 mm (1/8 to 1/4 in)

DUN COLOR: Wings: whitish. Body, females--olive abdomen, dark brown thorax. Body, males--dark brown.

SPINNER SIZE: 3-6 mm (1/8 to 1/4 in)

SPINNER COLOR: Wings--clear. Body, females--gray abdomen, black thorax. Body, males--black.

OTHER CHARACTERISTICS: Nymph--large triangular gill on second abdominal segment. Nymph and adult--three tails. Dun and spinner--hind wing not visible; bulky thorax