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.
Described by Hanson, J.F. (1942) Records and descriptions of North American Plecoptera. Part II. Notes on North American Perlodidae. The American Midland Naturalist 28, 389–407.