Pieris oleracea

from The Collaborative International Dictionary of English v.0.48

cabbage butterfly \cab"bage butterfly\ (Zool.),
   a white butterfly ({Pieris rap[ae]} of both Europe and
   America, and the allied {Pieris oleracea}, a native American
   species) which, in the larval state, devours the leaves of
   the cabbage and the turnip. See also {Cabbage worm}, below.
   [1913 Webster] cabbage worm