Why Do Ladybugs Gather in Massive Swarms?

Huge aggregations of ladybugs are an amazing sight to witness. . KQED Science

If you've ever gotten particularly lucky during a hike in the hills or mountains, you'll have stumbled across this spectacle. Thousands, even tens of thousands of ladybugs, crawling over each other in one huge clump. It's called an aggregation, and it's something these usually solitary beetles do each winter from about November to February.

Scientists believe ladybugs aggregate to regulate their internal body temperatures, share mates, enhance their defense, and share resources. Inside these aggregations, movement is disorderly rather than hierarchical, like a beehive or ant hill would be.

At the bottom of this file, you'll find a great video that shows what these aggregations look like and explains the science behind them.

Ladybugs swarm on radar

Ladybugs are known for their sense of togetherness other times of year as well.

In June 2019, a group of ladybugs moving through San Diego was so big, it showed up on the National Weather Service's radar. Meteorologist Joe Dandrea told the Los Angeles Times that the ladybug "bloom" appeared to be about 80 miles by 80 miles.

But the insects were apparently spread through the sky, not clustered together.

“I don’t think they’re dense like a cloud,” Dandrea said. “The observer there said you could see little specks flying by.”

Ladybugs are important beneficial insects to have around as they prey on aphids, an insect that can destroy gardens and crops. These red beetles are our best friends for healthy plants. Unfortunately, they seem to be in decline. You can help scientists keep track of the species' status by participating in a citizen scientist project called the Lost Ladybug Project.

View Article Sources
  1. Verheggen, François J., Heiko Vogel, and Andreas Vilcinskas. "Behavioral and Immunological Features Promoting the Invasive Performance of the Harlequin Ladybird Harmonia axyridis." Frontiers in Ecology and Evolution. 2017.