The joro spider has long, striped, black-and-yellow legs and a bedazzled rump. Full-grown, the arachnids can be as big as a grown-up human’s hand. And as babies, these spiders can fly through the sky on parachutes of silk, an ability that allows them to explore different areas.
“These spiders are very shy,” said Andy Davis, an animal ecologist at the University of Georgia. “They’re more likely to run away from you than to try to bite you.”
Joro spiders are native to Japan, and were discovered in Georgia in 2013. “At the time, they were only in a few counties, but now they’re all over the place and spreading fast,” said Davis. Recently, Davis conducted a study to estimate how far these spiders might be able to spread. The results were surprising.
First, Davis learned that the animals are resistant to cold temperatures that might kill a more tropical species. Next, he looked at the climate in areas where joros are common in Japan and tried to match that to the climates in the United States. Putting both bits of information together, Davis estimated that the spider would be able to survive across much of the East Coast. In fact, they might be there already.
Joros are really good at hitchhiking on cars, said Davis. And remember, when they’re tiny, these spiders can soar on the breeze.
“Lots of orb-weaving spiders do this,” said Davis. “When the babies emerge from the egg sacs, they send up a silk thread into the air and catch the wind.”
Known as ballooning, this behavior helps spiderlings travel hundreds of miles or even thousands of miles. But only the babies can do it, said Davis, so people almost never see it in action. That also means you don’t need to worry about huge spiders falling out of the sky.
While nonnative species can sometimes cause problems in ecosystems, joro spiders don’t seem to be much of a nuisance. In fact, they like to eat other nonnatives, such as the spotted lanternfly and brown marmorated stink bug. So having joro spiders around might be a good thing.
Rather than fearing the spiders, Davis recommends using them as an opportunity to explore nature. They’re peaceful creatures and big enough to watch as they weave their webs or catch insects to eat.
“That spider could be there for a few months, so give it a name like Mabel or Jessica, and throw some [insects] in there for it,” said Davis. “You can take care of it just like you would a butterfly caterpillar.”