Scary But Shy Joro Spiders Spread To US Gardens, Parking Lots

Scary Joro spiders the size of a human hand are spreading across the U.S. Eastern Seaboard and heading north.

The East Asian species is named after the mythical Japanese creature Jorogumo, which can turn into a beautiful woman and trap men with silk. With blue-black and yellow stripes, long legs and sometimes a splash of red, Joros may look terrifying but are actually quite shy.

"They're not dangerous. They're not aggressive. Even if you ... go after the spider and harass it to such an extent that it would bite you, it wouldn't be an issue," said Daniel Kronauer, an associate professor at Rockefeller University.

Most spiders freeze for less than a minute when disturbed, but Joros can shut down for more than an hour, University of Georgia researchers found.

First spotted in the United States in the state of Georgia a decade ago, female Joros can grow as large as 8 inches (20 cm) across, and males 4 inches (10 cm).

Joros, which are native to China, Japan and Korea and can survive in the Himalayan foothills, probably came to the U.S. on trade routes, Kronauer said. "Most of these invasive species get spread around by humans, often in cargo ... that's carried by ships as ballast."

Since then, Joros have steadily spread throughout the Carolinas, Virginia and Maryland, Kronauer said. "They're pretty cold tolerant. ... That's why we can expect them to move further north."

The impact of Joros on the U.S. ecosystem is uncertain, though they tend to do very well in parks, gardens and parking lots, Kronauer noted. "There's a good chance that maybe this summer we'll see some of them in New York."

But fear not, Joros are unlikely to bite humans or pets. They much prefer to eat pesky mosquitoes, roaches, wasps and other insects.