TL/DR –
The Joro spider, a large, brightly colored invasive species native to East Asia, is spreading across the South and East Coast of the United States. Despite public concern, spider experts say the species poses little risk to humans, while the increasing prevalence of invasive species that damage crops and trees is a greater worry. Researchers predict the Joro spider will eventually spread across much of the continental US due to global trade and climate change, which are creating more hospitable environments for such pests.
The Joro Spider: A Growing Population in the US
The Joro spider, an eye-catching invasive species, is expanding across the United States. Though their growth has led to panic, experts suggest it’s unwarranted.
“People like the weird and fantastic and potentially dangerous,” explains David Nelsen, a biology professor who has studied the spread of Joro spiders. “This is one of those things that sort of checks all the boxes for public hysteria.”
The real concern lies in the increasing prevalence of invasive species that damage crops and trees, amplified by global trade and climate change.
“I think this is one of those ‘canary in the coal mine’ type species where it’s showy, it’s getting a lot of attention,” says Hannah Burrack, professor and chair of the entomology department at Michigan State University. Fruit flies and tree borers pose more threats than these spiders, she adds.
What is the Joro Spider?
The Joro spider, one of the orb-weavers, has bright yellow and black coloring and can grow as long as three inches. They are native to East Asia but are now seen across the US, primarily during August and September.
Where are they headed?
David Coyle, assistant professor at Clemson University, says the spiders’ central population is currently in Atlanta and expanding to the Carolinas and southeastern Tennessee. A satellite population has established in Baltimore over the last two years. Their spread to the Northeast remains uncertain.
Can they fly?
Yes, but only the young ones. Using a technique termed “ballooning”, young Joro spiders can travel long distances by using their webs to catch the wind and electromagnetic currents. Adult spiders, however, do not fly.
What do they eat?
Joro spiders eat anything that lands in their web, mostly insects. This could cause competition with native spiders for food, but could also feed native bird species. As for the hope that they could help control the invasive spotted lanternflies? Coyle says there’s “zero chance.”
Are they dangerous to humans?
Joro spiders have venom like all spiders, but they aren’t deadly or even medically relevant to humans. At worst, a Joro bite might itch or cause an allergic reaction. They tend to stay out of humans’ way.
What could cause damage to humans is the widespread introduction of other creatures like the emerald ash borer or a fruit fly called the spotted wing drosophila that threaten natural resources.
Andy Davis, a research scientist, states “This is just one more example of mankind’s influence on the environment.”
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