They have large heads with well developed mandibles, cylindrical bodies and short powerful legs. Many species build houses from gravel or vegetable matter. Some of these houses are stationary, many are mobile. Other species roam unencumbered in the substrate. Still others build and trap food with spider type webs.
Some species are herbivorous others are predacious.
Caddis larva come in a wide range of sizes and colors. Laval populations of many species go through predictable behavioral drift cycles where they are consumed by trout and white fish in great numbers. When the larva has reached maximum maturity it crawls into a protected niche and constructs a cocoon. Metamorphosis starts to change the larva into an adult insect. It develops wings, feelers, long legs and sex organs.