While most people think the San Juan worm fly is specific to the San Juan River, the truth is there are aquatic worms in many rivers and fish are not shy about eating them. There are purists who say this is worm fishing. Fact is the San Juan Worm fly imitates a worm just like Muddler imitates a sculpin. This fly also won the prestigious One Fly Tournament in Jackson Hole, Wyoming. Keep a few worm flies in the box and you won't be sorry. Tied on a #12 hook.