Everything we know about the Joro - the giant flying spiders multiplying across the East Coast

The spiders may be big and frightening to some, but they don’t pose a threat to humans

Graig Graziosi
Wednesday 06 April 2022 02:04 BST
Related video: Kentucky wildlife officials use electrofishing to fight invasive species

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Louise Thomas

Louise Thomas


Americans living on the East Coast may soon find themselves faced with an invasion of hand-sized, venomous spiders that can fly using their webs. But, at least for now, there's no reason to fear our new eight-legged neighbours.

An invasive spider species called the Joro has made inroads in Georgia. Big, bright, and capable of weaving webs ten feet deep, the spiders have already managed to freak out some Georgians who have had first hand encounters with the arachnids.

But will the spiders pose a problem as they continue to spread throughout the eastern US, or will they simply be a bright new addition to the nation's diverse catalog of fauna?

What is a Joro spider?

Joro spiders are big, at least by US standards. The creatures can grow to 3 inches, and have colorful blue and yellow markings on their bulbous bodies, with red markings on their undersides. Their size makes them comparable to the Carolina Wolf Spider, which is the largest wolf spider in the country.

Huntsman spiders, another invasive spider species from Asia which now lives in subtropical regions of Florida, Texas, and California, have larger leg spans but smaller bodies than the Joro.

The spiders are native to Japan and are believed to have traveled to the US as stowaways on cargo ships. Entomologists believe the spiders will be able to survive the cold temperatures of East Coast winters thanks to their fast metabolisms. Because they can survive the cold, they will likely become a permanent fixture in North America.

Joro spiders weave thick, golden webs, and can even use their silk as a sort of parachute that allows them to float through the air to new locations. While that feature allows to to traverse some distance, researchers believe the Joro will likely spread throughout the rest of the US in the same manner they arrived here in the first place; hitching a ride with traveling humans.

Are Joro spiders dangerous?

Only if you're a small insect, like a mosquito or a crop-destroying brown stink bug. While the spiders do hunt using venom, their bites are not harmful to humans.

Despite their namesake - the mythical Japanese Jorōgumo, a spider that can turn itself into a beautiful woman to feast on unsuspecting men - the spiders don't pose any real threat to humans.

If a Joro were to bite a human or a pet, it may not even register, as the spiders' fangs are believed to be too small in most instances to break skin. Bites that do register pain have been compared to bee stings.

The most alarming aspect of the spiders is almost certainly their size, as most Americans are not accustomed to seeing large spiders out in the wild. Their webs are proportional to the spiders' size, and may be intimidating to those who encounter them without knowing about the Joro. Compounding the fear some may experience when encountering a large spider is the fact that they tend to live in groups, meaning it would not be unreasonable for someone to find not just one Joro, but several.

Unfortunately for arachnophobes, the spiders also tend to set up their webs near the edges of forest and alongside people's houses, so the chances of encountering one if you live on the East Coast is fairly high.

Andy Davis, a research scientist in the Odum School of Ecology at the University of Georgia, told NPR that the best thing for people to do if they encounter the spiders is to just leave them alone.

"If they're literally in your way, I can see taking a web down and moving them to the side, but they're just going to be back next year," Mr Davis said.

Will they harm the US ecosystem?

While any new species can upset the balance of an ecosystem, entomologists have not been ringing alarm bells over the new spiders.

Some invasive species prompt calls from local officials to kill them on sight due to the threat they pose local ecosystems. Last year, officials in New York, Pennsylvania, and Ohio called on residents to kill any spotted lanternflies they saw on sight, as the bugs feed on over 70 types of trees and plants. If left unchecked, the insects would cause substantial harm to regional flora.

The Joro spider does not appear to pose that same threat, according to entomologists. If anything, they may be a beneficial addition to the US ecosystem as they tend to eat biting pest insects. Further, they may prove a fruitful source of food for birds and other larger predators.

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