Dictionary
rail'road worm"
the larva of a fruit fly,
Rhagoletis pomonella, that burrows through apples, forming tunnels that sometimes appear on the skin as faint depressions or darkened trails: a serious pest of apples in colder regions of North America. Also called
apple maggot. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.