The large, scary-looking Joro spider that can make massive webs is popping up again in multiple states, but researchers say the invasive species is essentially harmless to humans.
The spider species native to East Asia was first spotted in the U.S. in Georgia in 2014. Since then, sightings have been reported in more than a dozen states, primarily in the Southeast.
The adult female Joro spiders are yellow with bluish-green stripes and black and yellow legs. Their bodies can be up to 1 inch long and they have a leg span up to 4 inches. Males are smaller and mostly brown in color.
While they have been referred to as flying spiders, you won’t see one of the large adults soaring through the air. Researchers say only the young spiders are capable of something called ballooning, where they release silk that catches in the wind, carrying them long distances — a technique that’s not unique to this species.
So far this year, Joro spiders have been spotted in Georgia, the Carolinas, Tennessee and Alabama, according to public trackers.
The Great Smoky Mountains National Park, which sits on Tennessee’s border with North Carolina, told 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.
Reports of sightings will help researchers at the University of Tennessee who are mapping the spread of the species, the post says.
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, a University of Tennessee graduate student conducting spider surveys in the park, explained why the spiders should be left alone.
Primarily: It’s illegal to disturb wildlife in national parks.
But, even outside the park, Jones doesn’t encourage people to kill the spiders because there’s not yet enough research to know if they are doing any harm to the ecosystem, she said.
She is currently researching how the presence of Joro spiders impacts native orb-weaver populations. Leaving the spiders where they are helps with that research, she said.
Additionally, the Joro spider looks like some native spiders, so it’s easy to mix them up, she said.
“We just want to kind of discourage people from killing them anytime they see them,” Jones said. “Not only do we not know what they’re doing, but they are also very easily misidentified — our natives are very easily misidentified as invasive.”
Sightings outside of the national park can be reported to iNaturalist or other data collectors.
Massive webs but minimal harm to humans
Joro spiders are 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.
Stuart Cahill/Boston Herald via Getty Images 
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 also 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.
