Monarch Butterfly Migration
In North America, monarch butterflies make yearly migrations to warmer southern regions during winter, returning to the north during spring. No individual butterfly survives long enough to make the full trip.
The average lifespan for summer-born butterflies is less than two months, which is not long enough to make the lengthy journey to overwintering locations in Mexico and California. However, the last generation of summer enters a non-reproductive state known as diapause. In this state, individuals can live for more than 7 months.
During diapause, the butterflies migrate to warm southern regions, in order to avoiding the freezing northern winter. They have been known to cover entire trees completely while hibernating. Once winter is over, diapause ends and the fertile butterflies return back on a spring migration.
On their way back north, the now exhausted butterflies lay their eggs and die. These eggs hatch and mature, and continue the journey. It takes up to four generations of monarchs to make it back to their original location.
Luna sin estrellas, Ken Schneider, Heather Spaulding on Flickr