The Elk Hair Caddis Fly is one of the most productive dry flies for Brook Trout. It resembles little Caddis Flies and Stoneflies, both of which are popular Brook Trout meals. This fly will catch fish throughout most of the year, but it will be most successful during a hatch. A hatch is when flies are transitioning from the early stages of life, to an adult. Flies gather in large groups on the water, resulting in a lot of Brook Trout gathered in the same location.If you find yourself a hatch, throw an Elk Hair Caddis fly into the water and you’ll probably have something on the line shortly thereafter.