Egg
Adult swallowtails lay their round, cream-colored eggs on plants that the larva can eat once hatched. This species lays single eggs, though other butterfly species are known to lay them in clusters.
Larva
Swallowtail caterpillars spend most of their time eating and gathering up energy for the pupa stage. These insects are commonly found in weedy areas such as meadows and fields, according to the University of Kentucky Entomology Department. To protect themselves from predators, swallowtail caterpillars are able to secrete foul chemicals that both smell and taste bad. The larva can reach up to 2 inches in length.
Pupa
After several molts, or shedding of its exoskeleton because of increasing size, the larva enters a dormant period known as the pupal stage. The caterpillar will hang upside down from a plant and spin a silken cocoon around itself. Within the cocoon, tremendous changes take place as the caterpillar morphs into its adult form. Black swallowtails, like most other butterfly species, usually spend the winter as a pupa, emerging in the spring as adults to begin the cycle once more.
Imago
When it emerges, the adult, or imago, has a large abdomen and limp, droopy wings. It will hang upside down from its chrysalis to help drive fluid into its wings to fill them out. Once the wings are dry, the adult will eliminate the waste it has built up during the pupa stage and then fly off to mate.