Like stoneflies, caddisflies are notable for many different species and for their ability as larvae to indicate good water quality. In the case of caddisflies, their low tolerance for pollution is what makes them a good indicator. They can be affected by both chemical and biological conditions.
The larvae of many caddisfly species use silk to make protective cases, which are often strengthened with gravel, sand, twigs, bitten-off pieces of plants, or other debris. You can see this phenomena represented in the drawing here, at right. See the Caddisfly Nymph itself in the illustration on our main Take Action page, in the Color & Learn panel.
Artwork by FRWA member Mary Budkoski