MIGRANTING MONARCH BUTTERFLIES AT SANCTUARY IN MEXICO, 2002-02-15 (photo)

Thousands of Monarch butterflies are seen among the trees at the Sierra Chincua sanctuary at the Monarch Butterfly Biosphere Reserve, in the state of Michoacan, on February 15, 2002. In January a cold snap killed an estimated 270 million butterflies at the reserve, where they arrive after their yearly winter migration from Canada and the United States. The death toll, between 40 to 80 percent in some of the colonies, has raised questions among scientists, who now believe they have have grossly underestimated the number of butterflies that migrate to Mexico. REUTERS/Henry Romero/FEATURE/MEXICO-BUTTERFLIES HR/GN