A spectacular secret that went undiscovered for 40,000 years lies revealed in splendor in the cool pine forests in central Mexico.
It is the wintering ground of hundreds of millions of giant Monarch butterflies, whose annual odysseys from Canada and the northern United States defies the laws of nature.
The pine-clad, 10,000-foot mountains in the central Mexican state of Michoacan are not easy to reach. But once there, a traveler finds a breathtaking fantasy world where the Monarch truly reigns.
The land and sky turn orange and black--the Monarch's colors--as the hand-sized butterflies flutter in the air like autumn leaves, cover every inch of every Oyamel (fir) tree branch, envelop every bush and blanket even the rugged paths cut out for curious lepidopterists.
With a broom, a local Indian brushes thousands of Monarchs from the path to clear a way for visitors, who tiptoe in awed silence among them.
Hundreds on the path are dead, half-eaten by birds or lizards, or trampled by humans.
Others on the ground are mating, while many are simply exhausted from their flights of 2,000 to 3,000 miles from the cold of their winter mountaintop.
Enlivened by the sun's rays--they use their wings as solar-energy panels--the Monarchs seek new basking spots, falling like glittering sequins on the heads, hats or clothes of their human visitors.
If the sun is shrouded by clouds, they flutter back to their trees, turning the green mountaintop forests into a spooky landscape of orange and black.
The Monarch is unique among butterflies, surviving tough, long, high-altitude flights with a hardiness that strong birds would envy.
Monarchs that are found west of the Rocky Mountains winter in California, where they face danger because many of their traditional sites have been bulldozed by land developers.
Those found in the East congregate in October in the Great Lakes area, awaiting favorable flying weather and a tail wind to help them to Mexico. Pilots have reported seeing them gliding or flying at between 10,000 and 12,000 feet.
Their transcontinental flight, at an average of 10 miles an hour, takes up to six weeks, as they rest at night.
After reaching Michoacan, where the government has declared 11 areas protected sites, they rest or mate.
Most males die soon afterward, leaving the females and their offspring to make the long flight north alone at the end of March. In fact, most of the births take place along the way, particularly in Texas, where the females lay up to 300 eggs each, usually on the underside of milkweed leaves.
Most of newborns who survive will take part in the next migration south, and some of their mothers may survive part of the cycle.
In a strange natural phenomenon that science cannot explain, the Monarchs begin their return home each year exactly on the day of the spring equinox. Experts believe that a certain position of the sun must arouse their instincts.
Zoologist Fred Urquhart of the University of Toronto began studying Monarchs in the 1930s. A collaborator, Ken Brugger, eventually found them on the Michoacan mountaintops on Jan. 9, 1975.
Mexican butterfly lovers and ecologists say that the number of Monarchs wintering here has diminished in recent years and that those butterflies who do arrive seek out higher ground to escape increasing encroachment by humans.