Wintering Monarchs in Mexico.
Photo: © Flickr user rainasun

Since the Monarch butterfly's wintering grounds were discovered in Mexico in 1975, scientists have been trying to figure out how the butterflies navigate to such a precise location. Migrant butterflies, newly emerged from their chrysalids, fly 2,000 miles to a forest in the mountains where they have never been. Even more remarkable, millions of butterflies from locations throughout the eastern United States and Canada all meet in an area of only 70 square miles.

Through genetic studies, Professor Steven M. Reppert of the University of Massachusetts Medical School seems to have found the keys to how Monarchs migrate. Reppert and his colleagues identified two cryptochrome proteins, CRY1 and CRY2, in Monarchs. CRY1 functions as a blue light receptor, allowing light to reach cells that control the circadian clock. The newly discovered CRY2 provides a feedback loop that keeps the butterfly oriented on its journey. Reppert is also spearheading an effort to sequence the entire butterfly genome. His current research compares gene expression in migratory and non-migratory butterflies.