There is a spider making a home in Southern California that’s the size of your palm and soars through the air riding the wind.
Although the Joro spider, an invasive species that has been spotted across the United States, including in California, isn’t dangerous, its size and the web it creates can seem like props from a horror movie.
“They’re not medically significant,” said Pat Wooden, the insect identification lab manager at Virginia Tech. “They’re great big bugs, but they’re not going to bite you and cause terrible damage. They’re established really well, so there isn’t a whole lot we can do against them. Their spider webs can get up to 10 feet.”
The spider has recently been found in California, with the first report in October, Wooden said. They don’t have any natural predators and have a big web that is able to capture a diverse range of prey, including beetles, wasps and stink bugs. The spiders are also good at distancing themselves from each other so they aren’t in competition.
Wooden recommends that people try not to panic and do nothing if they happen to see one. The spiders benefit humans by acting as natural pest control, eating mosquitoes, biting flies and invasive stink bugs. Their venom isn’t dangerous to people or pets and they seldom bite.
The spiders disperse themselves by “ballooning,” in which spiderlings release silk that catches in the wind, letting them travel. This falsely gives people the impression that the spiders can somehow fly.
“They’re incredibly prevalent and people interact with them a lot,” she said. “We’ve gotten past the people thinking that they flew, which was the real scary thing that came with them.”
The first time the spider was spotted in the U.S. was in Georgia in 2014, likely brought to the country through shipping containers from China, Taiwan, Japan and South Korea, Wooden said.
The spiders are especially prevalent in Appalachia and have also been spotted in South Carolina, North Carolina, Tennessee, Kentucky, West Virginia, Virginia, Maryland, Pennsylvania, Mississippi, Alabama, Ohio and Florida.
“We learned that we’re just going to be stuck with them,” Wooden said. “They’re becoming more prevalent and they’re slowly making their way across the Southeast. When we recently did work in Tennessee, every single rock alcove had one in it.”
The University of Georgia College of Agricultural and Environmental Sciences and Warnell School of Forestry and Natural Resources find the spider so intriguing that they launched a website, Jorowatch.org, to track where the spiders have popped up across the country. Most have been reported in Georgia. The website shows some spiders reported as recently as October in Santa Barbara County.
According to the website, the spiders are active from September to October and are orb-weavers known for spinning spiral wheel-shaped webs. They can be identified by a yellow abdomen with red markings, and by the golden color of their webs.
Male Joro spiders are about 0.25 inches in size and mostly brown while female spiders are about 1.25 inches and mostly yellow.
The spiders’ white egg sacs, usually laid between October and November, are often attached to leaves, tree bark and flat structures and contain 400 to 500 eggs, according to Jorowatch.
