Mass Migration of Painted Lady Butterflies Entrances Californians

Swarms of Painted Lady butterflies are being sighted all over California. Some scientists are pointing to this years abundant rainfall in the desert regions on the Mexican border. Another reason being considered is the recent boom in plant growth seen in southern California. The super bloom of colorful wildflowers in 2017 have been a magnet for both tourists and butterflies alike.

By Julia Jacobs

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.

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.

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