Joro Spiders Are Flying All Over the Southeast and Headed Up the Coast

An invasive spider has arrived in the United States, and it’s quickly spreading throughout the Southeast and heading up the coast.

The yellow and black spider is a member of a group of spiders called orb weavers, so named because of the wheel-shaped webs they create. At the beginning of its life cycle, the Joro is the size of a grain of rice, but adult female spiders can grow legs as long as 3 inches when fully extended.

While this might be great news for spider enthusiasts, what does the influx mean for the rest of us? Do they bite? How will they affect our health and the environment? Keep reading for everything you need to know about the Joro spider.

How Did the Joro Spider Get to the U.S.?

The Joro spider is a native of Asia, specifically Japan and other countries along the western Pacific Rim. It’s uncertain how the spiders arrived in the United States, but experts suspect they arrived in northern Georgia as “stowaway hitchhikers” on international shipping containers.

Scientists suspect that happened around 2010, and they’ve now spread into at least five states: Georgia, the Carolinas, southeastern Tennessee, and Maryland. Researchers believe Joros will continue to spread north up the East Coast, but it’s unclear how long that could take — anywhere from a few months to a decade.

What Do Joro Spiders Look Like?

Male and female Joro spiders look different. The females are easier to identify: Their bodies can be more than an inch wide, and they’re bright yellow with blue-green bands and a distinctive red mark on the bottom of their abdomen. Their legs, up to 3 inches long, are usually black with yellow-orange bands, but in rare cases they are all black. Males are significantly smaller — less than one-third the size of females, with a brown body, elongated abdomen, and yellowish stripes.

Where Are You Likely to Spot a Joro Spider?

Right now it depends on where you live. If you live in a state where the Joro spider has “landed,” they do appear to be spreading fast, said David Coyle, PhD, an assistant professor and spider expert at Clemson University in South Carolina, in a press release.

A study that assessed the Joro’s potential habitat range concluded that the spider will eventually inhabit most of the eastern United States.

That same research found that these spiders could be comfortable in both the city and the countryside. Joros have been regularly spotted in areas that spiders native to the area typically don’t inhabit, weaving their golden webs high up between power lines, on top of spotlights, and even above pumps at gas stations.

Mature females can spin webs 10 feet or wider, with support strands that can reach over 20 feet.

The Joro May Be the World’s ‘Shiest’ Spider

If you’ve heard that Joro spiders are “invasive,” don’t be alarmed. It doesn’t mean they are aggressive or dangerous — they’re not. “Invasive” in this instance means that the species has been introduced to a new ecosystem, and has the potential to cause problems for the environment. Whether that will end up being true is still being evaluated by researchers.

In a study that looked at how the Joro spider reacts to potential threats (delivered by a brief puff of air), researchers found that the spiders remained “frozen” for over an hour after the stimulus. This is highly unusual, given that the average spider moves within just one minute, leading investigators to suggest that the Joro is “the shiest ever documented.”

Do Joro Spiders Bite?

As predators, almost all spiders, including the Joro, have venom, but very few are poisonous to humans, says George Uetz, PhD, a professor at the University of Cincinnati in Ohio and a spider expert.

The good news: Joro spiders aren’t known to bite people.

Researchers at the University of Georgia have collected hundreds of the spiders, let them crawl in their hair and wander on their arms, and the experts even interacted with the spiders’ webs. The result: No bites from the spiders, which they described as “timid and non-aggressive.”

If for some reason you do get bitten by a Joro, it may itch or cause an allergic reaction, but it’s not deadly.

Another reason a bite is unlikely: Joro spiders aren’t likely to want to come inside, says Dr. Uetz. “They are very sedentary in their webs,” he says.

What Do Joro Spiders Eat?

Initially, experts thought the species may be beneficial because it eats the marmorated stink bugs and spotted lanternflies that are destroying trees on the East Coast. In fact, they will eat just about any insect that gets caught in their web, including moths, flies, mosquitoes, bees, wasps, beetles, and roaches.

So while they may eat a few harmful bugs, there’s no chance that the Joro will make a significant dent in the lanternfly population.

Can Joro Spiders Really Fly?

Baby Joro spiders can take flight using a method called “ballooning,” a technique in which they use their webs to harness the wind and electromagnetic currents of the earth to carry them to new locations.

Adult Joro spiders, on the other hand, have to rely on their eight legs to get around.

It’s Not Clear How Joro Spiders Will Impact the Environment

Because the spider eats whatever it catches, butterfly or stink bug, their presence can’t be easily labeled “good” or “bad.”

One pattern is emerging: Where there are a lot of Joro spiders, you don’t find other spider species. That means Joros are displacing native spiders, and what that means in the long term is unclear, experts say.

What if My Dog Eats a Joro Spider?

It’s unlikely that your dog will get sick if it eats a Joro spider, says Uetz.

How to Deal if You’re Scared of Spiders

Most spiders, the Joro included, are harmless, says Uetz.

“Approach them from a distance, observe them, and you will see they are no threat, as they stay in their web,” he says.

Given the spider’s shy nature, there’s little chance that one will want to come near you. A Joro spider is likely to freeze, allowing you plenty of time to make your escape.