Tricos: "The New Phonebook Is Here!"

Yes, they are mostly predictable. But as Bob Messeroll points out in The Missoulian, a mass of fallen Trico spinners is enough to get anyone’s adrenaline flowing.
“Usually by noon or so, the water will be littered with spent trico spinners, at which time the trout will begin to feed rhythmically, almost hypnotically. I can’t do justice to the sound of trout sipping tricos, but if it doesn’t fill you with a sense of fishing urgency, nothing will.”