Fist-sized Joro spider spreading north, but only insects need fear

They can grow as large as a child’s hand, travel through the air hanging by a thread and could soon be landing in a backyard near you.

But as the Joro spider, an invasive species, makes its way across the Eastern Seaboard, experts said there’s no need to fear — they’re harmless to humans and pets. And despite their intimidating size, they are quite docile, experts said. Their bodies can range from 1-1½ inches wide and counting their leg span, can stretch a total of 3-4 inches long.

“There’s no reason to panic. That spider is still not here in New York, and if it makes it to New York, it is not going to pose a problem or a risk to people. It's not a spider that is going to chase you and try to bite you,” said Alejandro Calixto, director of New York State Integrated Pest Management at Cornell University.

As with all spiders, they are venomous, but their venom is only harmful to other insects it preys on. People would not be hurt by its bite, according to experts. Females are bright yellow and gray and can grow bigger than males, which tend to be smaller and brown.

Native to Eastern Asia, they arrived in Georgia in 2014, likely from an overseas shipping container. They have since taken up residence in several other southeast states, including South Carolina, North Carolina and Tennessee. They were also reported in Alabama, Oklahoma and West Virginia, and were even spotted as far north as Baltimore, Maryland, according to David R. Coyle, a Clemson University assistant professor who in November published a study forecasting how far the species can spread as well as ecological impacts.

Coyle found that just as the Joro has quickly settled into states in the south, they can also weather colder Northeast winters.

But when or whether they will arrive in New York is harder to predict. Spiderlings can traverse long distances via a mechanism called ballooning, where they release gossamer threads and float through the air.

According to a Penn State Extension at The Pennsylvania State University, Joro spiders travel at a rate of 10 miles per year, but can cover hundreds of miles via ballooning. Experts said they could also move around faster by hitching a ride on someone or something.

“It might get [to New York] this year, if it's brought in by some sort of human-transported hitchhiking event, or it might be a decade before it gets there,” said Coyle, who works at Clemson University’s Department of Forestry and Environmental Conservation. He added it might not arrive at all. “It's impossible to tell.”

Joro spiders, or Trichonephila clavate, which belong to a family called orb weavers, are known for creating elaborate webs 10-12 feet wide and which can be quite sturdy. In one 2022 study, a cardinal perched on a web and stole the spider’s prey.

Experts like Coyle said they’re monitoring what impact the Joro spider will have on the ecosystem as they reduce the number of native orb weavers.

“The threat we see, on top of being just really annoying and pestiferous in places where there's high populations, is that we are seeing negative impacts on native species,” Coyle said.

“Where we've got these high Joro populations, the populations of native orb weavers are way down.”

Any sightings in New York should be reported to New York State Integrated Pest Management and confirmed because they could be confused with the similar-looking golden silk orb weaver, native in the southeast. 

“Once we confirm the spider, that spider can be just removed by using a broom or a vacuum,” Calixto said. He urged people not to use pesticides.

Dan Gilrein, extension entomologist at the Cornell Cooperative Extension of Suffolk County, said despite the spiders naturally slow pace, a sighting in the region wouldn't be surprising. 

“Given the way these spiders are moved around in vehicles, etc. we could see this arrive on Long Island sooner than later,” Gilrein said in an email.