Nature

15 February 2011 03:20 am

Monarch butterflies line a branch of a bush in the Pedro Herrada butterfly sanctuary on a mountain in the Mexican state of Michoacan February 1, 2011. Monarch butterfly colonies in Mexico more than doubled in size this winter after bad storms devastated their numbers a year ago, conservationists said on February 14, 2011 although the migrating insect remains under threat. Millions of butterflies make a 2,000-mile journey (3,200 km) each year from Canada to winter in central Mexico's warmer weather but the size of that migration can vary wildly. Picture taken February 1, 2011. REUTERS