At the end of every summer, more than 100 million monarch butterflies (Danaus Plexippus) sweep across North America to overwinter (4,750km further south) in California and Mexico. No single individual makes the entire round trip, as the duration of these journeys exceeds their lifespan. Instead, the females lay eggs during the migration, from which the next generation of migrants emerges. (https://go.nature.com/2NUvncC)