Mass Migration of Painted Lady Butterflies Entrances Californians

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Painted lady butterflies landing on a cherry tree as they migrated north through Encinitas, Calif.CreditCreditMike Blake/Reuters

By Julia Jacobs

March 17, 2019

Swarms of any other insect might provoke fears of a coming apocalypse, but clouds of butterflies migrating through Southern California are captivating onlookers who are relishing the otherworldly spectacle.

The orange butterflies, called painted ladies, are known to travel annually from the deserts of Southern California to the Pacific Northwest. This month, people are taking notice because of the sheer size of the migration: Scientists estimate the teeming painted ladies number in the millions.

Substantial rainfall in the deserts near the Mexican border, where the North American painted ladies lay their eggs, is the reason for the unusually large swarms. The rain caused plants to thrive, giving the painted lady caterpillars plenty of food to fuel their transformation, said Arthur M. Shapiro, a professor of evolution and ecology at the University of California, Davis.

Butterfly in the skkkyyy... #paintedladies @WindwardSchool pic.twitter.com/4YYV107br0
— Dr. Melanie Arias (@20thC_Melanie) March 12, 2019

To human observers, the painted ladies move with speed and intention, as if they have somewhere to be. They can fly as fast as 25 miles per hour.

“The striking thing is they’re moving very rapidly and directionally,” said Professor Shapiro, who has studied butterfly migrations in California for more than 40 years. “So it’s almost like being in a hail of bullets.”

They tend not to veer from oncoming cars, which can prove troublesome in Los Angeles traffic. When the painted ladies smash into a windshield, the result is a glob of yellow, butter-like ooze. That’s the result of the butterfly’s stored fat, used to make the long journey north, Professor Shapiro said.

Monika Moore, a butterfly enthusiast who lives in Fullerton, Calif., said she noticed that the mass moves in a strange way. The butterflies will fly low to the ground in an open field or yard, but when they encounter a tall building, they will fly over it — creating a “funky” up-and-down dipping pattern, said Ms. Moore, who has a Facebook page called California Butterfly Lady.

“They’re in a hurry, like the rabbit in ‘Alice in Wonderland,’” she said. “They have a very important date.”

This year, the painted lady migration in California appears to have veered off its customary course. Professor Shapiro said that if the painted ladies were following their annual pattern, they should have arrived in Northern California about a week ago, yet they appear to be staying in Southern California.

One possible explanation, Professor Shapiro said, is that there has been such abundant rain and plant growth in Southern California that the butterflies have settled down and reproduced there.

Professor Shapiro reported on Sunday evening that he had seen nine painted ladies near where he lives in the Northern California.

“Presumably these are the vanguard,” he wrote in an email. “We’re off and running.”

The explosion of plant growth in Southern California that has fueled this migration of butterflies is in itself a spectacle. The growth of colorful wildflowers, called a super bloom, has attracted a steady stream of tourists. In 2017, wildflower blooms in Southern California were so dense that they were visible from space.

[One of our reporters visited Anza-Borrego Desert State Park, a site of the super bloom.]

Substantial rainfall in the deserts near the Mexico border, where the North American painted ladies lay their eggs, has fueled this year’s unusually large swarms.CreditJohn Francis Peters for The New York Times

Although this year’s butterfly migration is significant, it pales in comparison with the swarms of 2005. That year, scientists estimated more than a billion butterflies traveled across California. Cars on California highways looked as if they had been splattered with raw eggs.

As the painted ladies linger in the southern part of the state, Californians are getting a prolonged look at the clouds of flapping orange wings.

On an overcast day last week, Jessica McGhee biked to the waterfront in Redondo Beach to collect plastics to use to make art. Ms. McGhee said she saw a couple of butterflies flit by, then a few more. Soon they flew by in the dozens, and then in the hundreds.

“I just sat and watched them for like two hours,” she said. “I felt like I was in a Disney movie.”

Follow Julia Jacobs on Twitter: @juliarebeccaj.