Like other butterflies and moths, Monarch butterflies undergo complete metamorphosis, meaning that they have an egg, larva (caterpillar), pupa (chrysalis), and adult stage. The egg and caterpillar stages occur only on species of native milkweed (genus Asclepias), whereas adults survive by nectaring on a variety of flowering plants.
Monarch butterflies have a migration pattern that allows them to range from northern Mexico where they over-winter, to Canada where they spend some of the summer, then to Mexico again to spend the winter. But the same butterfly does not make it through the entire cycle.
In the spring, the first butterflies leave Mexico and begin flying north, living two to five weeks while laying eggs as they fly through Texas nectaring on flowers. The second group of Monarchs emerges from the eggs in Texas, and continues north, laying their eggs and dying in Oklahoma, Kansas, and Nebraska. This cycle of emerging, flying north and laying eggs continues in the summer for three or four generations of Monarchs. Many reach as far north as Canada.
As fall begins, the final generation of Monarchs stops mating and changes their metabolism so they can live long enough to fly all the way back to Mexico, over-winter by hanging in the trees with thousands of other Monarchs, and then start the journey north again in the spring. These final adults can live up to nine months.
Much of the Monarch information was obtained from https://monarchjointventure.org/monarch-biology/life-cycle.