The Collaborative International Dictionary
Cankerworm \Can"ker*worm`\, n. (Zo["o]l.) The larva of two species of geometrid moths which are very injurious to fruit and shade trees by eating, and often entirely destroying, the foliage. Other similar larv[ae] are also called cankerworms.
Note: The autumnal species ( Anisopteryx pometaria) becomes adult late in autumn (after frosts) and in winter. The spring species ( Anisopteryx vernata) remains in the ground through the winter, and matures in early spring. Both have winged males and wingless females. The larv[ae] are similar in appearance and habits, and belong to the family of measuring worms or spanworms. These larv[ae] hatch from the eggs when the leaves begin to expand in spring.