sci-universe: Each fall, millions of North American monarch... February 28, 2015 at 06:55PM

sci-universe:

Each fall, millions of North American monarch butterflies migrate to California and Mexico for winter. They make a massive journey (up to 4,830 kilometers/3,000 miles) and use the sun to ensure that they stay on course. On cloudy days Earth’s magnetic field as a kind of backup navigational system. (read more here)