Caddisflies are different from mayflies and stoneflies because they pass through complete metamorphosis-Egg, Larva, Pupa, and adult stages. The larva often form cases that they carry with them for protection. However, there are also free-living caddis which do not have cases. both types play an important roll in a trout’s diet. The majority of their lives is spent as larva on the stream bottom. At maturity many build cocoons-like structures where they pupate. When conditions are right the pupa swim to the water’s surface and emerge as adults. caddis hatches often start in the evening and continue long into the night. Caddis adults are available all summer and into the fall, and the larval stage is available year round to trout.