The oversized, striking Joro spider — known for spinning enormous webs and startling homeowners — is showing up again across several states. Despite its intimidating appearance, scientists say this invasive spider poses little threat to people.
Native to East Asia, the Joro spider was first documented in the United States in Georgia in 2014. In the years since, reported sightings have spread to more than a dozen states, with most concentrated across the Southeast.
Adult female Joro spiders are hard to miss: they are bright yellow, marked with bluish-green stripes, and have long black-and-yellow legs. Their bodies can measure up to 1 inch, while their leg span can reach about 4 inches. Males are much smaller and are generally brown.
Although Joro spiders are sometimes called “flying spiders,” full-grown adults are not gliding through the sky. Researchers say only young spiders use a process known as ballooning, releasing strands of silk that catch the wind and carry them over long distances — a dispersal method used by other spider species as well.
This year, Joro spider sightings have been reported in Georgia, North Carolina, South Carolina, Tennessee and Alabama, according to public trackers.
Great Smoky Mountains National Park, which straddles the Tennessee-North Carolina border, warned visitors Tuesday that the spiders “may be hanging in a web near you.”
“The invasive joro spider has been slowly spreading through the Smokies, and we need your help to track its whereabouts,” a post on the park’s Facebook page says.
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The park said public reports will support University of Tennessee researchers as they map the continued spread of the Joro spider.
What to do if you see a Joro spider
If you see one of the spiders in Great Smoky Mountains National Park, take a picture and report it through the iNaturalist app or email UTKJoroProject@utk.edu, the park says.
Despite it being an invasive species, the park says not to disturb the spiders.
Caitlin Jones, who identified herself as one of the researchers in the comments of the park’s post, explained why the spiders should be left alone.
Primarily: It’s illegal to disturb wildlife in national parks.
But another reason is spiders that are native to the region, including other orb-weavers, can easily be mistaken for Joro spiders.
“We also don’t know what they are actually doing to our native orb-weavers,” Jones wrote in a comment. “That’s my area of research and my reason for leaving them when I see them.”
Outside of national parks, it may not be illegal to kill the spiders, but it’s not necessarily encouraged either. Sightings can also be reported to iNaturalist or other data collectors.
Massive webs but minimal harm
The spiders are a natural pest control and currently don’t appear to harm crops or trees like some other invasive species.
Joro spiders are also unlikely to bite humans, according to a study published last year in the Journal of Medical Entomology.
Researchers examined spider-human interactions in what they believe to be the first controlled study of spider bites.
“During these interactions, spiders primarily moved to avoid human contact, and bites were incredibly rare, mainly occurring when spiders were forcibly restrained,” the researchers said.
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When bites were forced to occur, “recipients of bites reported low levels of pain, and other symptoms associated with the bite were highly localized and transient,” the authors of the study wrote.
The spiders are unlikely to go inside homes, researchers said, but they might make large webs — some stretching up to 10 feet in diameter — on the outside of houses or other structures. If they are a nuisance around your home, experts have recommended using a broom or stick to move them and their web far away from where they were.
