Monarch butterflies start migration to Mexico

John A Pavoncello
York Dispatch
The annual fall monarch butterfly migration is underway, with many of the notable orange and black butterflies making their way through Pennsylvania on their long journey to central Mexico, Monday, September 12, 2016. John A. Pavoncello photo

Each fall, while the leaves change color and the temperatures start to cool, flocks of geese for large V's in the sky as they migrate south. Local hot spots, including Rocky Ridge County Park and Hawk Mountain, draw hundreds to watch birds of prey follow the geese, heading south for the winter. But normally not noticed by the avid bird watchers, brilliant orange and black monarch butterflies flit and flutter south, some traveling farther than many waterfowl.

Monarch butterflies, Danaus plexippusare the only butterfly known to two-way migrate, heading south on fly-ways much the same as waterfowl and spending the winter in central Mexico.

"What most people don't know" says Professor Karl Kleiner, a biology teacher at York College, "is that the monarchs they see anytime in the summer are the descendants, the daughters, the granddaughters, grandsons and great-grandsons of monarchs that wintered down in Mexico."

According to Kleiner, monarchs stop reproducing in the fall during their migration, with some butterflies traveling 3,000 miles to their wintering grounds in the mountains of Mexico.

After spending several months in Mexico, the monarchs start their return trip, starting to breed along the way. Each successive generation travels a little farther north, until monarchs that are three or four generations from the original migrating butterflies reach the mid-Atlantic states, including Pennsylvania.

The migration is tracked each fall and spring by the US. Department of Agriculture, and nature lovers are encouraged to help by counting and identifying the location of migrating monarchs via the web at:  or with the Journey North App available on the App Store and Google Play.