ScienceDaily: Each fall millions of monarch butterflies from across the eastern United States begin a southward migration in order to escape the frigid temperatures of their northern boundaries, traveling up to 2,000 miles to an overwintering site in a specific grove of fir trees in central Mexico. Surprisingly, a new study by scientists at the University of Massachusetts Medical School published in Current Biology, suggests that exposure to coldness found in the microenvironment of the monarch's overwintering...