The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Back before I started my first real field season as a graduate student working on Chinook salmon in the Chena River, I took a fun personal trip up to the North Fork just after ice-out (yes, the ice breaks up that late here!) to collect some Alaskan insects to photograph for the site.