Four stages of life, egg, caterpillar, pupa, and adult butterfly. Four days for an egg to hatch. Three to five days for a caterpillar to molt. After four moltings, the fifth instar of the caterpillar sheds its skin and forms its chrysalis. Ten to fourteen days for a pupa to emerge from its chrysalis. Four generations each year, but only the fourth adult butterfly lives longer than six weeks and migrates to warmer regions.