Invasive Joro Spiders Spotted In Bucks Co.: What To Know

BUCKS COUNTY, PA — Giant Joro spiders have officially moved into Bucks County, according to a research center that monitors invasive species.

These arachnids, which can grow to the size of a human palm, have been spreading north since being first spotted in Georgia in 2014. The Joro spider’s venom doesn’t pose a danger to humans or pets, though its sheer “unusually large” size can be frightening alone.

There were six Joro spiders seen at a resident's yard in Northampton Township on Sept. 5, according to Joro Watch — an interactive monitoring program developed by the Center for Invasive Species and Ecosystem Health.

A local entomologist confirmed the sighting (which appears to be the only Joro spider sighting in Pennsylvania at this time) several days later.

This species, which is native to East Asia, craft wheel-shaped webs and is part of the orb-weaver family of arachnids.

The Mid-Atlantic states would make sense as a breeding ground for the spiders, as the region is the same latitude as places in Asia where they thrive. The species can can survive a brief freeze that kills off other spiders and has about double the metabolism of its relatives, according to one study.

Female Joro spiders are easily spotted, as they are brightly-colored with red, blue and yellow hues. The body of an adult female of this species can be over an inch long — with a four-inch leg span, according to Scientific American.

Male Joro spiders are brown, and grow to about a quarter of an inch, according to Joro Watch.

They are most commonly seen building large webs in September and October, and the females lay egg sacs beginning in mid-October through November, the Joro Watch website explains.

Joro spiders also use wind currents to travel while parachuting, a method of silk production that allows them to travel in the wind. They don't exactly fly, but seeing one parachuting or "ballooning" through the air might make you think they do.

It's also possible that Joro spiders may actually be beneficial and prey on the invasive spotted lanternflies that have become a pest in southeastern Pennsylvania, said Valdosta State University biologist Erin Grabarczyk.

What To Do If A Joro Spider Moves In To Your Backyard

Despite their startling appearance, researchers say that Joro spiders are docile and shy, and do not pose a threat to people or pets. If you do get bitten, the bite would not require medical attention unless you have an allergic reaction, Grabarczyk said.

“They are not going to hurt you," Grabarczyk told Scientific American. "They are not going to hurt your kids, they are not going to hurt your pets.”

Andy Davis, a University of Georgia scientist, told Scientific American that the spiders are better left alone, and don't threaten agriculture in the way lanternflies do. He said seeing a Joro spider could even be "an unprecedented educational opportunity" for nature enthusiasts and for kids.

"Show your kids that spider," he suggested. "Show them what spiders do."

If you do want to get rid of Joro spiders that may be spinning webs around your home and garden, researchers at the University of Georgia said certain insecticides are effective against them, including Zevo Spider and Wasp spray and Green Light Insecticidal Soap.

Or, you could use a broom, rake, or long stick to take down both the web and the spider.

"The manual technique of wrapping them up in the web and stepping on them is very effective," UGA researchers said. "Simply destroying the web is not effective, as they rebuild in short order. Moving them to another area where they are less problematic can work but that has to be a good distance away or they will come back."