Joro Spiders Spreading Across the U.S. Eastern Seaboard

Joro spiders, known for their size comparable to a human hand, are spreading across the U.S. Eastern Seaboard and heading north.

Origins and Appearance

The East Asian species is named after the mythical Japanese creature Jorogumo, which can transform into a beautiful woman and trap men with silk. Joro spiders have blue-black and yellow stripes, long legs, and sometimes a splash of red. Although they look terrifying, they are 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.

Behaviour and Characteristics

While most spiders freeze for less than a minute when disturbed, University of Georgia researchers found that Joros can remain still for more than an hour. Female Joros can grow as large as 8 inches (20 cm) across, while males reach up to 4 inches (10 cm).

Arrival and Spread in the U.S.

Native to China, Japan, and Korea, Joro spiders can survive in the Himalayan foothills. They likely arrived in the U.S. via trade routes, according to Kronauer. “Most of these invasive species get spread around by humans, often in cargo that’s carried by ships as ballast.”

First spotted in Georgia a decade ago, Joro spiders have since spread throughout the Carolinas, Virginia, and Maryland. Kronauer explains, “They’re pretty cold tolerant. That’s why we can expect them to move further north.”

Ecological Impact

The impact of Joro spiders on the U.S. ecosystem remains uncertain. However, they thrive 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.”

Despite their intimidating appearance, spiders are unlikely to bite humans or pets. They prefer to feed on mosquitoes, roaches, wasps, and other insects.