Butterflies are insects that undergo complete metamorphosis. There are four stages in their lifetime which are egg, larva, pupa and adult respectively.

1. Since a butterfly larva only feeds on specific plants, a female butterfly only oviposits under the leaves or buds of its host plants. 

2. After the egg hatches to a larva, the latter starts to feed on the host plant. The larva of a butterfly needs to shed its skin for 3-6 times, and the last shedding is called pupation. 

3. The larva undergoes complex reorganization in the pupa. After the adult's structures have matured, it will undergo emergence. This process is called "eclosion".

4. After emergence, the adult needs to pump fluids into the wings to expand them and let the body temperature rise during daytime before being able to fly.