Definition of orange dog in US English:

orange dog

noun

US
  • 1The larva of the giant swallowtail butterfly, Papilio cresphontes, which feeds on the foliage of orange and other citrus trees.

  • 2(In full "California orange dog") the larva or adult of the western swallowtail, P. zelicaon.

Origin

Late 19th century.