Are ‘giant, flying’ joro spiders really taking over the U.S.?
With a jet black body and bright yellow markings, joro spiders look scary. But scientists say they’re actually pretty shy.
Judging by news headlines, the arrival of joro spiders in the United States means everyone is doomed.
“Giant venomous flying spiders… heading to New York area,” says CBS News. “East Coast braces for invasion of palm-sized venomous spiders capable of flying,” echoes Fox Weather. And The Guardian calls the arachnids “gag-inducing.”
Of course, the scientists who study Trichonephila clavata, which are native to east Asia, say such descriptions are misleading at best.
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Floyd Shockley, an entomologist and collections manager at the Smithsonian National Museum of Natural History in Washington, D.C., says he’s “mortified” by some of the sensationalist headlines. “There’s no evidence that they’ve made it to New York.”
While it’s true that joro spiders arrived in Georgia in 2014 by unknown means and can survive in the U.S., their colonization of North America isn’t exactly imminent.
So far, the spiders have been seen in Georgia, the Carolinas, Tennessee, and Oklahoma, with a few tiny satellite populations in places such as Maryland and West Virginia.
Widely misunderstood
Threats posed by these arachnids have been routinely exaggerated. For instance, a Gothamist article describes the spiders as having “a body about four inches long and legs that span six to eight inches—about the size of a human hand.”
“That is completely ridiculous,” says Shockley. “You’d have to stretch this thing out like a medieval torture device to get [its legs] even four inches, let alone six inches.”
Adult females max out at about four inches and are black and bright yellow in color. Males are much smaller and less colorful.
What’s more, during the summer months, every joro spider in the U.S. is no larger than a grain of rice. Adults die each winter, with eggs hatching in the spring and starting the cycle anew.
With so much misinformation afoot, here’s a breakdown of some of the other claims that often circulate online.
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Can joro spiders fly?
“The way those headlines are written, it makes it sound like they’re the monkeys in the Wizard of Oz,” says David Coyle an assistant professor and invasive species expert at Clemson University.
In truth, none of the large adult joro pictured in news stories are capable of flight. However, as spiderlings, joro and many other spiders can take to the skies in a common dispersal process called ballooning, which is different from jumping spiders.
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“Right after they hatch, the little hatchlings may be the size of a sesame seed,” says Coyle. “Some of them will get up high and they’ll raise their abdomen. They’ll put a few strands of silk out, and some of them will get carried away by the wind.” Yes, just like in Charlotte’s Web, they build webs to spirit away.
“I hate to tell people, but every spring, there’s probably thousands of little spiders ballooning over your head, and people have no idea it’s happening.”
As for their “flying” to new states, Shockley says “they have expanded their range, but it’s not surprising for an introduced species in 10 years to have moved, you know, a state.”
He adds “we still don’t really know anything about how they would [survive] northeastern winters because, obviously, they’re not there yet.”
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Are joro spiders venomous or poisonous?
This is actually a bit of a trick question, since “spiders are predators and use venom to capture their prey,” says Shockley.
This means that nearly every spider on Earth is venomous, save for two small families of spiders that have lost the ability to produce venom.
The real question is whether an animal is venomous in a way that could harm people. For U.S. spiders, that is an incredibly small category that includes black widows and brown recluses—not joros, whose venom is non-toxic to people, he says.
In fact, the few reports of joros biting people suggest it’s like something between the itchy irritation of a mosquito bite and the pain of a bee sting.
Are they dangerous to humans?
Despite being relatively large and brightly colored, the joro spider is kind of a pushover.
“Based on my research, they’re really shy,” says Andy Davis, a research scientist at the University of Georgia. “If you leave them alone, they’ll leave you alone, and you can both go about your business.”
In a study published in the journal Arthropoda, Davis found that when threatened with a puff of air, native spiders froze for about 96 seconds before resuming their spiderly duties.
Joro spiders, on the other hand, didn’t move again for more than an hour, making them the most timid arachnids on record.
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“I have held joro spiders dozens of times,” adds Coyle, who has never been bitten. “My kids have held them. They’re typically very docile.”
“They’re just big and scary-looking to a lot of people, but that doesn’t necessarily mean they’re mean or have malevolent or malicious intent.”
The truth about joro spiders
However unwelcome joro spiders are in the U.S., some experts say it’s time to get used to the new neighbors.
“This is a tough sell,” says Davis, “but maybe, instead of trying to do away with them, people should just maybe sort of learn to live with them. Because their spread is exponential at this point. Like, there’s millions upon millions of them.”
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As far as their impact to the environment, it’s likely a mixed bag. Joros eat other invasive species, including brown marmorated stink bugs and spotted lanternflies. They also eat fruit flies. However, there’s some evidence they’re outcompeting native spider species.
Even so, Coyle doesn’t see much reason to kill them on sight.
“If it sparks joy, smash them,” he says. “Are you going to do any measurable impact whatsoever to the [joro spider] population? No, you’re not.”
