Biology
The Biomechanics of Long-Distance Migration in Monarch Butterflies and Orientation Mechanisms
Quick fact
Monarch butterflies use a time-compensated sun compass: they determine direction by comparing the sun's position with an internal circadian clock, allowing them to fly southwest in the fall despite the sun's movement across the sky.
Why this is interesting
Every autumn, millions of monarch butterflies vanish from North America, only to reappear in the mountains of Mexico—a journey of over 4,000 kilometers. How does a fragile insect with a brain the size of a pinhead navigate such an epic migration?