An unusually large population of migrating painted lady butterflies has been swarming over the Los Angeles area in recent days, and they're headed our direction.

The butterfly species, Vanessa cardui, also known as the cosmopolitan butterfly, migrates annually from the deserts of Southern California to Oregon, and due to the superbloom down south this year, their numbers grew wildly.

As UC Davis ecology professor Arthur Shapiro tells SFGate, the last similar painted lady butterfly boom was in 2005, and the swarm made it to Northern California by March 11. This year they're a couple days off of that, but flying at 25 miles per hour with few stops, they're likely to start showing up any day.

Painted ladies, with their orange and black coloring, are often mistaken for monarch butterflies, but these have distinctive beige, white, and brown patterns on the undersides of their wings.

Shapiro says swarms like these are like ancient plagues of locusts, only we like butterflies better because they eat weeds and not crops. He imagines this swarm is about the same size as 2005's, around 1 billion.

The butterflies are likely to primarily stick to the Central Valley in their route north, Shapiro says, though some will likely appear around the Bay Area.

Below, some of the social media evidence of the swarm.