The Caddis Larva imitates the premature nymph stage of a Caddis fly coming to the top of the water . Being a staple of a trout diet, and often an indicator of water quality. The Caddis Larva is an excellent go to fly. The best time to use is almost all year around especially during a Caddis hatch. Can be fish by itself underneath an indicator or as a dropper on a double dropper setup. My favorite way is dry dropper setup. With a size 14 deer hair Caddis as a dry, and Caddis larva size 18 as a dropper. 5X through 7x tapered leader and tippet are excellent choices.