Atlas Obscura and The Monarch Butterfly

"Each year, as winter gives way to spring, tens of millions of monarch butterflies leave the safety of their wintering grounds in central Mexico and migrate north. But the history behind how the global scientific community finally came to understand the unique role that this part of Mexico plays in the lifecycle of monarchs is just as fascinating as the butterflies themselves."

https://www.atlasobscura.com/videos/gaze-upon-a-million-monarch-butterflies-in-mexico

More Monarch Butterflies Return to Mexico

PIEDRA HERRADA, MEXICO

A monarch butterfly perches on a branch in the Piedra Herrada sanctuary near Valle de Bravo, Mexico, last week. CHRISTIAN PALMA AP

More Monarch butterflies appear to have made the long flight from the U.S. and Canada to their winter nesting ground in western Mexico, raising hopes after their number dropped to a record low last year. But experts still fear that unusual cold temperatures will threaten the orange and black insects.

The temperate climate of the mountains west of Mexico City normally creates an ideal setting for the Monarchs. Every fall, tens of millions of the delicate creatures fly thousands of miles to their ancestral breeding grounds, creating clouds of butterflies. They clump together on trees, forming chandelier shapes of orange and black.

The sanctuaries have become tourist attractions, especially in the peak months of January and February.