The following is a key to insect larvae feeding internally in apple fruit. Several morphological terms should be reviewed.
Caterpillars have six true, jointed legs on the thoracic segements, immediately behind the head.
These prolegs have small hooks, or crochets . High magnification is required to examine these structures. Brooks, F. E. 1924. The cambium curculio, Conotrachelus anaglypticus Say. Tortricid fauna of apple.