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Tricorythodes stygiatus

Tricos start life as an egg. The eggs develop when the water temperature is fifty five degrees and above. Eggs laid last fall went dormant, or into diapause. This spring when the water temperature hit fifty five degrees again, they began developing again.

Eggs take about forty five days to develop into a nymph.

trico nymphs inhabit aquatic vegetation, lack hind wing pads, move by crawling, and are the least important stage for the angler, although they are often abundant during periods of behavioral drift.

When hatch time comes, (usually around July fifth), the nymphs begin to congregate in the “cushion” (the slow water on the bottom.)

DUNS (sexually immature adults)

Between 10pm and 2am the males (black abdomens) change to duns on the bottom, bob to the surface (with their momentum helping them penetrate the surface film,) and fly to the vegetation.

Females (light olive abdomens) hatch the same way at first light


Body size 3-3.5mm. Size 24.

Tails are at least 3 times longer than the body.

Three to six mm long wings are about 1 mm longer than the


A few hours after first light, the duns (change to spinners (sexually mature adults). Males and females swarm over the stream mating almost immediately.

Some spinners take off before shedding the dun coat. [flight hatch]

After mating, the female either returns to the foliage to “plump” its fertilized eggs prior to oviposting, or drops immediately to the surface to extrude egg packets on the surface.

Great swarms often hover above the water with the peak at mid-morning, and falling spent by late morning

Look for them over canopied riffles. Female spinners (white abdomens) on the bottom of the swarm, mating males (black abdomens) and females in the middle of the swarm and all males on the top of the swarm.

The first ones to die and fall onto the surface film are the females, followed by males and females, followed by all males. The trout go nuts! Some anglers tie only white abdomens preferring to color them black when the males hit he water.

Since the trout are high in the water column their window is very small. A trout one inch below the surface has window of only two inches in diameter.

Casting accurately is a must!

I find success increases as tippet size goes down. The difference between fish and no fish is 6x and 7x. The difference between fish and lots of fish is 7x and 8x,

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