Females are wingless, which means they can migrate only by walking. The females lay eggs in the spring or fall, giving them their common names. They crawl from the ground up tree trunks to lay eggs on the branches. Larvae or caterpillars of both species hatch from egg masses in the spring when trees are just reaching budbreak and new foliage is expanding. The larvae grow to approximately 1-inch long and are quite slender.
Color is extremely variable, with light and dark forms in both species.
Both are striped longitudinally with green, brown and pale yellow colors predominant. However, the drab colors make them blend with tree branches, which they resemble when they sit still. Larvae feed for about 3 or 4 weeks before they drop to the ground to pupate in the soil, usually in late May or early June. Cankerworms remain in a pupal state in the soil until the adults emerge in the spring or fall, depending on the species. They are a nuisance when they drop to the ground because they leave silk threads trailing from the trees.