The Invasive Joro Spider Is Getting Cozy in the U.S.

joro spider
Scientists confirmed the first known occurrence of the Joro spider (Trichonephila clavata) in North America in 2013. Wikimedia Commons (CC BY 2.0)

An invasive species of spider is making itself comfortable in parts of the southern and eastern U.S. But don't let the Joro spider give you the creepy crawlies just yet. Between its golden webs and its silk-swinging tactic to track down a mate, this arachnid is a fascinating and, as far as we know, harmless (unless you're a stink bug) addition to the ecosystem.

And we may as well get used to the bright yellow Joro spider because it looks like they are planning on taking up permanent residence. Research from the University of Georgia suggests the invasive arachnids can exist in colder climates than previously thought and, therefore, could spread through most of the Eastern Seaboard of the U.S.

“The way I see it, there’s no point in excess cruelty where it’s not needed,” said Benjamin Frick, co-author of the study and an undergraduate researcher in the school of ecology, in a press release. “You have people with saltwater guns shooting them out of the trees and things like that, and that’s really just unnecessary.”

Where Do Joro Spiders Come From?

The Joro spider, scientifically known as Nephila clavata, is native to East Asia. In Japan, it's called jorō-gumo meaning "entangling or binding bride." In Korea, it's called mudang gumi meaning "shaman" or "fortune teller" spider.

The names reflect the beauty and intrigue of the orb weaver spiders. While the smaller drab male is nothing to write home about, the females feature a yellow and gray abdomen, bluish-green bands across the body, orangish bands on the spanning legs, and a bright red underbelly.

This spider, which can be as large as 3 or 4 inches (8 to 10 centimeters) long, can't actually tell your fortune, but it can weave a beautiful basket-shaped web that reflects gold in the sunlight and can be as wide as 10 feet (3 meters).

Joro Spiders Globalize as an Invasive Species

Along with commonly found electronics and bananas, exotic plants and critters like the Joro spider are known to hitchhike on America-bound commodities, especially in shipping containers.

Now, the Joro has jumped from the shipping container and exists in Georgia and parts of South Carolina, and has even been spotted in Tennessee and Alabama. Scientists expect them to reach New York and New Jersey in 2024.

In some cases, homeowners have hundreds of Joro spiders around their homes. They prefer to make their webs high in trees and have been found in forests, urban woods, porch lights, wooden decks, bushes, tall weeds and even on the vinyl siding of homes.

 Joro spider
A female Joro spider hangs peacefully in her web waiting for prey, seen here from below. Wikimedia Commons (CC BY SA 3.0)

Joro Spider Adaptation

Their ability to adapt to natural habitats and native species food sources in northern Georgia and South Carolina has allowed the Joro spider's numbers to swell across the east coast, reaching as far north as West Virginia. However, it's only a matter of time before predators catch up with the new invasive species.

"I think that the spiders have spread so quickly here because predators, parasites and diseases have not caught with them yet," said Professor Paul Guillebeau, professor of entomology at the University of Georgia, when we spoke to him in 2021. "If there is a new, large food resource like the booming spider population, something will take ultimately take advantage," he said.

How Joro Spiders Mate

Joro spiders live very close to each other, which helps individual spiders with the mating process, since males don't make their own spider webs, a function that is left entirely to the females.

To mate, the Joro spider male must pursue the females, albeit very carefully. Joro spiders may use gossamer and float, legs outstretched, on a breeze, from tree to tree or branch to branch, until a female Joro spider is within sight, or they spot a less male-occupied web.

"Then the male tries to find a receptive female. The male is almost always smaller, so it's tricky business to make your move without being eaten." Guillebeau has seen males around his house wait until a female is busy eating an insect before he gets close — a much safer approach.

Are Joro Spiders Poisonous?

Though Joro spiders were first spotted in Georgia in 2013 and people are somewhat worried at seeing so many of them so suddenly, it's still far too early to understand their big-picture impact on the environment. So far, however, the Joro spiders eat stink bugs and other flying insects, which is appreciated by farmers whose crops can suffer from stink bug infestations.

As orb weavers, they will naturally compete with other orb weavers like the golden silk spider for prey, but since they often weave their webs higher than local spiders, they may eat different kinds of prey, noted Guillebeau.

Joro spider bites are venomous, but they aren't dangerous to you or your pets. Joro spiders will also only bite you or your animals if they are scared enough to do so.

Joro Spiders Don't Threaten Human Activity

"Even if you walk into a Joro web, it will try to escape rather than attack you. If you catch a Joro in your hand, it may bite you out of fear. If I were caught by a giant, I'd probably bite," said Guillebeau.

If you do get a Joro spider bite, it may irritate human skin similar to a bee sting, but it's not as bad as a brown recluse (which actually isn't that bad) or black widow. There is currently no broad initiative to remove Joro spiders from the American ecosystem.

What should you do if you see a Joro spider (or any other spiders you may commonly catch around your house)? You may be tempted to kill this invasive species, but instead try being more curious, Guillebeau suggested.

"Have a look at it every couple of days. Show your children; they are fascinating to watch. Toss an insect into the web if you want to see them in action." Guillebeau reminded us, "Don't kill spiders (or anything else) for no good reason. We are all playing our role in the ecosystem."

Original article: The Invasive Joro Spider Is Getting Cozy in the U.S.

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