Caddis Fly, a mothlike insect found near ponds and streams. There are 1,000 species in North America. The adults range in length from ¼ inch to one inch (6 to 25 mm). They are brown or gray with two pairs of membranous wings; the wings and body are covered with fine hair.

The female lays the eggs in water. The eggs hatch into aquatic larvae called caddis worms. In many species, the caddis worm constructs a portable protective case around the lower half of its body. It uses its front legs to move about. The case is usually made of leaves, shells, and grains of sand cemented together with a gummy substance in the saliva. When fully grown, the larvae undergo complete metamorphosis. The larvae withdraw into the cases and seal the open end. After a few days they emerge as adults and fly away. Caddis worms are an important food of freshwater fish.

Caddis flies make up the order Trichoptera.