Like all insects which has complete metamorphosis the butterfly too has 4 stages of its life cycle. They are egg, larva (caterpillar), chrysallis (pupa) and imago (adult butterfly). However as you are aware the adult butterfly (or moth) has no mouth hence it cannot "eat" anything. The stage where the lepidoptera (butterfly and moth) eats the maximum is the caterpillar stage. It is always hungry. Here is a swallowtail cat polishing off a citrus plant ( Murraya koenigii ) leaf. Hope you guys like the photo, and please feel free to ask anything relating to the above!