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Insect Highlight: Trichoptera - Caddisflies

Updated: Feb 23

By Hope Chappuis

Caddisflies are a magical group of insects closely related to moths and butterflies, which can make silk from glands in their body and head. Caddisfly larvae build mini, case-like houses with silk, sand, pebbles, stones, and twigs to protect themselves in streams and rivers. The larvae, or immature stages, are aquatic, but the adults emerge from the aquatic environments to mate.

How do I identify a Caddisfly?

Caddisflies, which are in the insect order Trichoptera, resemble caterpillars but with a sclerotized or hardened head and thoracic plate (covers the thorax). Larval caddisflies can also be identified by the anal claw on the end of their long soft abdomen. Adult caddisflies have wings and long antennae and when resting, fold their wings over the top of their body, like a roof or tent.

Where can I find Caddisflies?

Caddisflies frequent cold, clean streams and rivers in freshwater habitats across the world. They can be recognized by their retreats and cases found many times under rocks. A good place to look for caddisfly adults is near streams on logs or rocks in the late spring or early summer.

Quick-fire Fun Facts

  • Trichoptera is the largest order of truly aquatic insects.

  • Caddisflies are often models for angler lures, as they are a tasty treat for fish. Fishermen also often search for areas where there is an emergence of caddisflies in the spring as the larvae of many species grow quickly when temperatures warm after lying dormant in the winter.

  • The retreat or case of a caddisfly can help to identify the taxon based on the material of which it is made.

  • Various species of caddisflies are also known to emerge as adults in winter.

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