Written by Peter Pearsall/Photo by Peter Pearsall

Perhaps you’ve seen a few of these butterflies recently, flitting about in your garden. Or perhaps you’ve seen hundreds, coursing along coastlines or crossing highways in steady streams, with many sadly meeting their ends splattered on car windshields and grills.

Measuring two inches from wingtip to wingtip, with black and white markings against an orange backdrop, these scale-winged insects are a familiar sight to people around the world. The painted lady (Vanessa cardui) is one of the most widespread butterfly species on the planet, found on every continent except South America and Antarctica.

In years of abundant winter rainfall, painted lady numbers can skyrocket, as early-blooming wildflowers provide nectar for butterflies and food sources for their larvae.

Like the famous monarch butterfly, painted ladies are migratory, following favorable conditions with the seasons. In the American West, these butterflies generally move in a north-northwest direction, leaving the Southwest and Mexico at winter’s end and traveling toward the Pacific Northwest with the onset of spring.

Painted ladies aren’t picky in their choice of plants to nectar on. Adults will use almost any plant in flower but they show preference for those in the Asteraceae family, including thistles. These plants are the butterfly’s hosts—their larvae eat leaves of asters and spin silken webs to protect themselves from predators.

Interestingly, painted ladies are known to breed and lay eggs in all seasons. A single year’s migration can involve several successive generations of painted ladies, each born and raised along the migration route.

It’s estimated that millions of these butterflies are migrating across North America this spring. Enjoy this natural spectacle while it lasts!