Feb. 6, 2008 - Ocampo, Michoacan, MEXICO - Monarch Butterflies mass at the Monarch Butterfly Biosphere Reserve in El Rosario central Mexican in Michoacan State. Each year hundreds of millions Monarch butterflies mass migrate from the U.S. and Canada to Oyamel fir forests in the volcanic highlands of central Mexico. North American monarchs are the only butterflies that make such a massive journeyÑup to 3,000 miles (Credit Image: © Richard Ellis/ZUMAPRESS.com)