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 Ross, H.H. & Ricker, W.E. (1964) New species of winter stoneflies, genus Allocapnia (Plecoptera, Capniidae.). Transactions of the Illinois State Academy of Sciences 57, 88–93.