The larvae of Monocesta coryli feed voraciously on elm leaves. Often the larvae leave the "ribs" of the leaf, and eat only the more tender parts.
Late in the summer the third-instar larvae drop to the ground and spend the winter under soil. Pupation occurs underground in April.
Below left: The egg masses contain about 30-50 eggs and may be found on the undersides of leaves, often near the tip.
Below right: An overwintering larva, rolled in a ball for protection and covered with soil.
More information about adult Monocesta coryli is elsewhere on this site.