Thousands of striking orange and black monarch butterflies began arriving to their winter home in central Mexico on Saturday (November 26) in their annual migration. The 4,800-kilometre mass migration of monarch butterflies in North America is one of the insect world's fantastic feats, with millions embarking on the arduous journey from as far north as Canada down into Mexico and the California coast each autumn. The number of migrating monarchs has plummeted in recent years.