Adults are a small fly with slender legs, Wings are mottled brown and cream and are held folded laterally over the back. The larvae live in cases made of seaweed and sand cemented together with the dark head and paler legs out of the case at one end.

Larvae are found in intertidal rock pools in sheltered areas. Adults are usually close to the waters edge and are often seen running on the rocks. They are not strong flyers and when they do fly it's very erratic.

Adult diet is unknown, it may be that like their freshwater cousins they don't feed as adults. The larvae feed on seaweeds especially coralline algae. Fish feed upon the larvae.

The only marine caddis fly in the world. Adults live only a few days. Eggs are laid on rocks amongst seaweed or in the arms of the cushion star which protect the developing larvae. The larvae live in their cases for up to 6 months. When ready to metamorphose the larva seals the case with silk and pupates for about a week, the adult bites its way out and flies off.

Photo Credit: Rod Morris. Photos available from www.rodmorris.co.nz