No single monarch butterfly finishes its migration — it takes four generations

Monarch butterflies in eastern North America fly up to 4,800 km to overwinter in a specific patch of Mexican forest their great-great-grandparents left the previous spring. Three or four short-lived generations make the northward journey over summer, then a single long-lived 'super generation' flies the entire way south in autumn, navigating by the sun's position and Earth's magnetic field despite never having made the trip before.

— Species account, Monarch butterfly migration — Danaus plexippus