Giant, yellow invasive spiders in SC ‘spreading like wildfire,’ new study shows. What to know
An invasive species of spider that arrived in South Carolina in recent years has spread fast and gotten a foothold in the Southeast, a new Clemson University study shows.
The Joro spider from Asia has spread through South Carolina and much of the Southeast, according to a new peer-reviewed study by David Coyle, assistant professor in the Department of Forestry and Environmental Conservation at Clemson, and several collaborators. The results of the study had one major takeaway.
“These things are here to stay,” Coyle said in a press release.
Also, the invasive spider is “spreading like wildfire.”
What is the Joro spider?
Before delving more into the study, it’s important to know a little more about spider itself. Thought to have arrived in the U.S. by a container ship, Joro spiders were originally seen in Georgia in 2014. They have long legs, a red belly and can grow to nearly 3 inches across with their legs spread.
Also, the spiders can form parachutes out of their webs, letting them fly from 50 to 100 miles in the wind.
Joro spider eggs usually hatch in late spring and the juveniles can be seen in early May. They lake to make their webs on just about everything, from homes, decks and porches to landscape plants.
The spiders and their webs will get larger through September, when the bigger adult females become very noticeable because of their bright colors. Males are drab brown in color and much smaller.
Joro study details
Advanced modeling techniques based on 20 separate variables were used in the study to assess the Joro’s native range. Those variables were then applied to the entire U.S. in an attempt to determine habitability elsewhere.
“Those data show that this spider is going to be able to inhabit most of the eastern U.S.,” Coyle said in the press release. “It shows that their comfort area in their native range matches up very well with much of North America.”
Findings show the spider present in the South Carolina Upstate and Midlands, as well as in Georgia, North Carolina and Tennessee — with reports also in Alabama, Maryland, Oklahoma and West Virginia.
“Barring some unforeseen circumstance, we expect the range of these things to continue expanding, likely to the north, and we’ve already seen that with some populations in Maryland,” Coyle said.
Are Joro spiders dangerous?
Southern Adventist University Professor David Nelsen, who led the research alongside Coyle, noted in the press release that the study shows Joros negatively affect native species. However, more research is needed to ascertain why and what can be done about it.
Coyle said that Joros have little interest in going into people’s homes, preferring to make webs outside of houses or other structures. And some initial opinions suggest Joro spiders may be beneficial by eating brown stink bugs and other nuisance species.
The truth is more nuanced.
“These spiders don’t seem to care what gets in their web; they’re just as likely to eat brown marmorated stink bugs as they are to eat a Monarch butterfly,” Coyle said in the press release. “To say they’re more beneficial than another spider is just simply wrong — they’re a spider — and if something gets caught in their web, it’s going to get eaten.”
If homeowners do feel inclined to remove a Joro from their property, standard pesticides will work, but they’re likely unnecessary.
“Pesticides work, but, also, they are probably overkill because it will kill everything else, and there is a cost involved; it’s just as easily to physically move them if they are on your house. So, I just tell people to take a stick or broom and remove them,” Coyle said.
