The Yellow Birdwing, just like all other butterflies, goes through four stages which is Egg (Ovum) , Caterpillar (Larva), Chyrsalis (Pupa) & Butterfly (Adult or Imago).
The adult female Yellow Birdwing, after mating with their male, becomes fertile and shortly after begins to lay eggs on its host plant which is the Aristolochia tagala; usually on the underside of the leaves or on other plants near/beside the host plant to protect its eggs from predators. In less than a week, it hatches as a caterpillar from the egg and most of the time, eats up its own egg shell to hide a trail of its presence.
Soon, the caterpillar would also chew on the leaves of its host plant. In the caterpillar stage, they can be subdivided for further identification into 5 stages from the 1st Instar to the 5th Instar. The caterpillar also sheds its old skin (known as moulting) between instars, so that it can grow bigger. It stays in Caterpillar stage for roughly about 3 weeks.
After that, it looks for a suitable place (can be on other plants) to begin a special transformation process. The caterpillar hangs itself upside down and within an hour or so, it turn itself into a chyrsalis/pupa. In here almost everything that resembles a caterpillar is broken down and then transformed into a butterfly. This is called the Pupa stage.
It remains in pupa stage for about 2 weeks. After that, the pupa hatches and a butterfly emerges / crawls out from the pupa. The butterfly hangs itself from the outside of the pupa to dry its wings and to pump fluid into the veins of its wings, expanding its wings to the fullest. The adult butterfly can then survive for about 2-3 weeks, whereby it can court, mate and lay eggs.
From our records, these are the average durations in the Yellow Birdwing's life-cycle:
Egg (Ovum stage): 5 Days
Caterpillar (Larva stage): 19-21 Days
Chrysalis (Pupa stage): 19-20 Days
Adult Butterfly (Imago stage): 14-21 Days