The Perfect Fly Green Sedge Larva is a trout fly that imitates the larva stage of life of the Green Sedge or caddisfly. The Green Sedge Larva is a free-living caddisfly larva that lives on the bottom of the stream and looks like a small, fat worm. They do not live in a case or have a shelter. They are commonly called Green Rock Worms. The fly should be fished on or near the bottom of the stream.