Joro spiders are invading the U.S. at an alarming rate

The southeastern United States is witnessing the fast expansion of an invasive arachnid species, Joro spiders, which is spreading at an alarming rate, according to a recent study from Clemson University.

First spotted in Georgia in 2014, these yellow-banded spiders have firmly established themselves across several states. A research team led by David Coyle, an assistant professor in the Department of Forestry and Environmental Conservation at Clemson, has delved into how pervasive the Joro spider has become and the potential scope of its expansion.

Joro spiders are here to stay

The researchers used advanced modeling techniques that accounted for 20 separate variables. The results suggest that the Joro spider’s native range aligns well with the climate conditions of much of North America. 

The implications of this finding are significant, with Coyle stating, “These things are here to say,” highlighting the expected continual northward spread of the species, already observed in areas as far north as Maryland.

Sailing into new locations

The Joro spider, distinguished by its large yellow body with a yellow and gray abdomen, employs a unique dispersal method called “ballooning,” which allows them to sail on air currents to new locations. 

This process has facilitated their spread across a vast area now spanning at least 120,000 square kilometers, encompassing Georgia, South Carolina, North Carolina, Tennessee, and reports from Alabama, Maryland, Oklahoma, and West Virginia.

Potential challenges for native species 

However, the rapid spread of the Joro spider comes with ecological concerns. David Nelsen, a professor at Southern Adventist University who co-led the research, emphasized the negative impacts on native species and the subsequent need for more research to understand and potentially mitigate these effects. 

And if the conclusion that a large area of the eastern United States may be habitable to Joros is true, Nelsen said, it may present a major challenge for native species and further stress already fragile ecosystems.

“Because of how far Joros have already spread and how fast they continue to spread, collaboration is vital for a project like this to succeed. Both collaboration across institutes and with local communities. I consider it one of our greatest successes that we have been able to assemble a team spread across the southern United States and partner with several non-academic groups and individuals,” Nelsen said.

Joro spiders are harmless to humans

Despite their non-native status and the potential ecological consequences, Joro spiders are harmless to humans. Coyle advises against using pesticides for Joro spider control, advocating for simple physical removal methods if they are found on structures. 

Their preference for outdoor habitats means that they are unlikely to venture into human dwellings, instead building their extensive webs on the exteriors.

Ecological impacts

There is an ongoing debate about the overall impact of the Joro spider. “These spiders don’t seem to care what gets in their web; they’re just as likely to eat brown marmorated stink bugs as they are to eat a Monarch butterfly,” said Coyle.

“To say they’re more beneficial than another spider is just simply wrong – they’re a spider – and if something gets caught in their web, it’s going to get eaten. And they don’t care if it’s a rare native pollinator and there are only a few of them left in the world or if it’s a brown marmorated stink bug. It’s six of one or half-dozen of another – it’s the same thing to that spider – it’s prey.”

Displacing native species

With this in mind, the ecological role of the Joro spider is very complex. The Clemson report noted that while the exact mechanisms of their spread are still being studied, one pattern is quite clear: Where you have an abundance of Joro spiders, you don’t find others. This means that Joros are indisputably displacing native species, the researchers said. 

“These are not just benign spiders coming to catch and kill bad things; these are pushing out native species and catching and killing whatever happens to get in their webs,” said Coyle. “Are they bad or good? It’s very nuanced depending on your perspective.”

More about Joro spiders 

Joro spiders are a species of spider known as Trichonephila clavata, which are part of the orb-weaver family. They are native to East Asia, particularly Japan, Korea, Taiwan, and China. These spiders are known for their distinctive, brightly colored bodies and large, strong webs.

In recent years, Joro spiders have gained attention in the United States because they have been spotted in the southeastern states, including Georgia. Their expansion is being studied for potential ecological impacts. 

Despite their size and vivid appearance, Joro spiders are not considered dangerous to humans, as their venom is not harmful to us, and they tend to be reluctant to bite. They do, however, play a role in controlling insect populations.

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