By Talia Avakian
March 13, 2019
David McNew/Getty Images

Millions of butterflies are taking to the skies of Southern California, creating a mesmerizing spectacle for onlookers.

People have begun posting photos of the colorful butterfly displays, which are occurring thanks to the migration of painted lady butterflies.

The medium-sized butterflies, also known as Vanessa cardui, are known for their orange wings and their ability to migrate long distances, which often occur sporadically and tend to be in large numbers following rainy periods in the deserts of the Southwestern U.S. and northern Mexico.

During periods where rains in the deserts are high, billions of the butterflies can be known to migrate, with Arthur M. Shapiro, a professor at the Department of Evolution and Ecology at the University of California, Davis' College of Biological Sciences, citing that 2005 was one of the biggest years for the migration so far with those in Sacramento able to see as many as three butterflies per second pass their field of vision.

The presence of increased rainfall and the wildflowers that have already sprung across California could signal higher numbers in the skies for this year, with Shapiro telling NBC News that “years of tremendous wildflower blooms typically are really big painted lady years,” and that he’s already received reports of migrations across San Diego, Pasadena, the Coachella Valley, at the Anza-Borrego Desert State Park, and in Temecula.

Before beginning their migration north, the butterflies will lay their eggs in the desert, with caterpillars feeding on vegetation in the desert (which is why having large amounts of rain can be so crucial) and growing through the late winter or early spring before taking to the skies, according to representatives from the National Wildlife Federation

The butterflies are able to store fat from the nutrients they acquire as caterpillars to enable them to make the journey north, with the butterflies able to fly all the way from Bishop to locations like Davis in just three days, according to Shapiro. The movement then reverses in August, when the butterflies head south back towards the desert grounds.

“We were seeing at least 100 of them a minute,” Doug Yanega, senior museum scientist at the University of California, Riverside’s Entomology Research Museum, told Los Angeles Curbed.

“That’s just looking out one window; we’re talking about a population in the millions, easily no question,” he added, noting that should the weather refrain from getting too warm or too dry, that the butterflies might even be able to be spotted in various locations as they make their way further north for the next few months. 

The migration is not unique to the U.S., with the butterflies known to create magnificent migration displays in Europe as they fly northward from North Africa, the Middle East, and central Asia.