Monarch butterflies live very differently depending on the generation. The common answer is:
- Summer generations: about 2–6 weeks as adults.
- Migratory (last) generation: about 6–9 months, spanning the southward migration, wintering period, and early spring return as they begin laying eggs.
Context and nuances:
- The long-lived migratory generation is sometimes called the “super” or “Matusalem” generation. This group delays reproduction and stores energy to undertake the full migration and overwintering cycle.
- In some sources, an even more conservative range for migratory adults is cited as roughly 6–9 months, with typical summer generations living only a few weeks.
- Real-world lifespans are influenced by temperature, nectar availability, predation, disease, and habitat quality along migration routes.
If you’d like, I can pull the latest scientific sources or conservation organization pages to pin down exact figures for eastern versus western populations and any recent updates.
