For thousands of years, millions of monarch butterflies have migrated from the northern U.S. and Canada to Mexico for the winter. But exactly how they know where to go is still a mystery.

Monarch butterflies are important culturally and ecologically across North America. Generations have watched in wonder as yellow-and-black striped caterpillars fold into green-and-gold chrysalises and ...

The rounded profile of a bird’s wing creates an airfoil, which generates lift and allows the bird to fly. But butterfly wings ... there are no land forms to slow the wind. In the Great Red ...