The presence of caddisfly larvae often indicates that clean, fresh water and a balanced, healthy aquatic ecosystem is present. Caddisfly larvae are a valuable food source for many aquatic organisms, and caddisflies feed on detritus within water sources. The diet of caddisfly larvae consists primarily of algae and plants, although some species eat smaller insects and the eggs of small fish. Some use their silk to capture food.
The bodies of caddisfly larvae contain eight segments. In some species, a set of gills is present. Caddisfly larvae carry six fully functional legs on their first three thoracic segments. The remaining segments in the rear of the abdomen contain hooks. They are capable of releasing silk from their specialized salivary glands and may appear similar to worms and caterpillars of the Order Lepidoptera.
Caddisfly larvae create protective cases from twigs, leaves and small rocks, which they glue together with their saliva. Caddisfly larvae conceal themselves inside these casings whenever danger is present. These cases house them until they outgrow them, at which point they molt their old cases and create new ones. Caddisfly larvae can molt as many as five times.