In the Northeast, tortoise beetles are occasional minor pests on potatoes and morning glories grown as ornamental flowers. In Vermont, they are most often beneficial in nature, feeding upon bindweeds, thistle, burdock, and other weeds. The adults chew a series of oval holes in the leaves. The holes are about the same size as the beetles. The larvae either chew holes like the adults or skeletonize the upper leaf surface, leaving a series of brown patches on the leaves.
Some species devour the entire leaf, especially on young plants.
The larvae on Canada thistle skeletonize the upper leaf surface. Tortoise beetles overwinter in the adult stage, hiding themselves in dry sheltered places under bark or trash. The adults emerge somewhat later in the spring, usually in the last half of May or early June. They are first noticed occasionally by their feeding, but more often by their brilliant colors during mating. Upon hatching, the larvae begin to feed.