It is easily recognizable by its bright orange-red wings, with black veins and white spots along the edges.
These butterflies congregate into colonies, clustering onto the pine and oyamel trees.
Its a remarkable sight that attracts scores of tourists.
Monarch butterflies are also one of the few insects which can cross the Atlantic.
Some believe the flight pattern is inherited.
The area is now a World Heritage Site known as the Monarch Butterfly Biosphere Reserve.
There are dozen such sites in Mexico and they are protected as ecological preserves by the Mexican government.
Unfortunately, the Monarchs overwintering sites are under threat because of massive deforestation.
The Monarchs migration is a natural marvel and for Mexico, a huge tourist attraction.
It would be a shame to lose it.
Sources:Wikipedia,NYTimes,Monarch-Butterfly.com,WorldWildlife
