Adults are small moths with a wingspan of 13mm. They are tan with grey markings and fringed wings.
Early instars mine leaves and are rarely noticed. Later instar larvae feed on leaves externally and camouflage themselves by holding a case at the end of the abdomen. The case, made out of leaves and silk, is approximately 6 mm in length.
Larvae feed on the inner leaf tissues causing small, rectangular spots between veins of leaves.
The Elm Casebearer begins feeding in the spring as soon as foliage appears. Pupation occurs in early summer and adults appear in mid summer. Eggs are laid on the underside of leaves usually among leaf hairs on the mid rib. After hatching, larvae burrow into the leaves and begin feeding on inner tissues. After the first molt, the larva exits the mine to construct an oval shaped case out of dried leaves and silk to cover its abdomen. Larvae continue to feed on leaf tissues externally, while holding the case at the end of the abdomen. In the autumn, larvae anchor themselves on to branches in small groups to overwinter.
Johnson, W.T. and Lyon, H.H. 2003. Insects That Feed on Trees and Shrubs. Second Edition. Cornell University Press, Ithaca, New York. 560 pp.