caddisfly

Caddisflies are insects in the order Trichoptera. They are freshwater relatives of moths, with about 7,000 described species in roughly 14 families found worldwide in streams, rivers, lakes, and wetlands. Adults are generally small to medium-sized and resemble moths, with hairy wings that are often held tent-like over the body when at rest. Most adults live only briefly and feed little or not at all.

The most distinctive feature of caddisflies is their aquatic larvae. Larvae spend most of their lives in freshwater ecosystems and exhibit diverse feeding strategies. The majority construct protective cases from silk and ambient materials such as sand grains, plant fragments, wood fibers, or snail shells, which they live in and extend from to move and feed. A smaller number are free-living or net-spinning and use silk to capture food particles. Larval diets range from detritus and algae to small invertebrates, and some are predators or filter-feeders.

Caddisflies undergo complete metamorphosis. Eggs are laid in water or on submerged vegetation; larvae hatch and go through several instars before pupating. Pupation typically occurs inside the larval case or in a sheltered retreat, and adults emerge to mate and disperse. Emergence can be seasonal and synchronized with environmental cues.

Ecologically, caddisflies are important in freshwater food webs: larvae contribute to leaf litter decomposition, nutrient cycling, and serve as a key prey item for fish and other predators. They are also widely used as bioindicators of water quality because many species are sensitive to pollution and sedimentation. In human culture, caddisfly larvae are valued by anglers for fly-tying materials.