Joro spiders are not harmful.
Joros are causing alarm because of their size, their numbers, and the fact that they are a non-native species. Also, they look like Halloween decorations come to life. But don’t worry; they’re not harmful to people, says Richard Hoebeke, associate curator of the arthropod collection at the University of Georgia’s Museum of Natural History and researcher in the university’s entomology department. All spiders have venom to subdue and digest their prey, but the Joro’s venom isn’t particularly toxic, unless you’re allergic to spiders. Joros are not aggressive, either. “Unless you faceplant into their webs, they won’t bother you,” Hoebeke says. “When a human comes around, they try to get out of the way.”
Joro spiders eat bad bugs.
Joros also appear to be acting as a beneficial insect. They’re chowing down on brown marmorated stink bugs, a serious agricultural pest that native spiders won’t eat, says Hobecke. “They’re good predators. They will feed on insects you don’t want around like yellow jackets, stink bugs, and mosquitoes.” And they don’t appear to be displacing any native spiders, he says. The first confirmed sighting of a Joro spider in North America was in Georgia in 2013. The spider has since spread across the state and has been reported in the neighboring Carolinas. “I strongly suspect they’re elsewhere and we just haven’t heard about them yet,” Hoebeke says. This year, the population of Joros has exploded in Georgia, with many people reporting dozens of Joro spider webs at their homes.
Joro spiders will probably spread.
It’s likely the spiders will spread beyond the Deep South to other parts of the country, Hoebeke says, because Joros’ eggs can survive cold temperatures of more northern climates. The spiders are also really good at spreading. Joros can hitch a ride on almost anything; a car bumper or cargo container. And they can lay their eggs on anything from a tree limb to outdoor furniture. The spiders also spread by ballooning, when they spin silk threads designed to catch a breeze and transport them on wind power. Joros can travel 50 to 100 miles that way. Joro spiders hatch in the spring out of sacs that contain hundreds of eggs. They grow to maturity over the summer and by early fall, they’re adult-size and weaving webs everywhere you look. The females are larger, about three inches across. You’ll see a female in the web she spins, sharing the space with one or more smaller male spiders that are her mates. The adults die off in the first frost of the season, so by late November they’re pretty much gone, leaving only their egg sacs behind. You can help UGA entomologists track the spiders’ spread and habits by sending in a photo of any Joros you see, making sure to include the date and location. And remember, “They suppress pests naturally, without pesticides,” says Hoebeke. “Having a bunch of them around is good.”
