Caddisflies are common around ponds, streams, and other slow-moving bodies of water. The female caddisflies deposit their eggs in the water. When the eggs hatch, the immature insects, called larvae, are aquatic. They live in the water and breathe with gills.
Some larvae are known as “free-living”. These larvae are often predators. They feed on other insects, minnows, and small invertebrates.
Many caddisfly larvae make protective shelters. They produce silk and fasten together sticks, small stones, abandoned shells, and other debris. They live inside these cases and add onto them as they grow.
Some caddisfly larvae use broken pieces or hollow sticks for their shelter cases. They simply climb inside the hollow stick and they have a shelter. When they are ready to move, they put their legs out and walk away. They carry the stick-shelter along with them when they go.
The purpose of the shelter is to provide protection from predators like fish. The larvae wait until the predators have passed by, then they start to move around. Experts suggest that caddisfly watching requires patience. It is necessary to wait until the larva starts moving. Until then, the larva often seems invisible in its camouflaged shelter.
When the larva is ready to change into an adult caddisfly, it simply seals itself inside the case. The larvae that develop late in the summer might not finish changing until spring. After it has changed into an adult caddisfly, the insect comes to the surface. There are often hundreds of new adult caddisflies near the pond. They find mates and start the life cycle over again.