#14: The Unexplained Migratory Navigation of the Monarch Butterfly
Each autumn, millions of monarch butterflies undertake a 3,000-mile migration to central Mexico, often to a location they have never visited. The butterflies’ great-great-grandchildren move precisely, even crossing busy highways and cities, with a brain smaller than a pinhead. Scientists believe that these tiny creatures use a genetic compass and an internal clock, but the exact mechanics are unclear.

