Longest migration of any creature: The Painted Ladies arrive in late March/April

By mid-to-late March, people in California and along the southern U.S. border should begin to see the world’s most persistent and breathtaking traveler: the Painted Lady butterfly.

The Painted Lady makes the longest known migratory journey of any animal, even longer than its celebrated cousin, the monarch, according to a study published in the Journal of the National Academy of Sciences (June 2021).

Found on every continent except Antarctica and Australia, the abundant Painted Lady makes a striking migration from Africa’s Sahara Desert to the Arctic Circle. Like the monarch, the migration spans generations. At least six generations are required for the butterfly to make the 9,000-mile trek. Similar generational journeys take the butterfly from southern roosts in Mexico to Canada.

But how do these delicate creatures cross such long distances? Scientists say they fly high (up to 2,000 feet) to catch and drift on favorable winds for long distances. In the late 1990s, weather radar in Denver detected a 70-mile wide swarm of these butterflies migrating in the fall — drifting north, not south — on the winds, according to the University of Colorado Boulder Museum of Natural History.

The number of Painted Ladies making the migration varies dramatically, and research has found it depends on the rainfall and the resulting abundance of plants.

This butterfly is abundant because it feeds on lots of plants — up to 300 host plants are known. It is constantly breeding, laying eggs, and flying, with each new generation taking up the trek according to season.