from
The Collaborative International Dictionary of English v.0.48
Cankerworm \Can"ker*worm`\, n. (Zool.)
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.
[1913 Webster]
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.
[1913 Webster]