- A large, brightly colored invasive species called orb-weaver spiders has been increasing in numbers in parts of the southern and eastern United States for years, leading some researchers to believe it’s only a matter of time before they spread across much of the continental United States.
- This spider is native to East Asia and its venom is not dangerous to humans.
- Scientists say the orb-weaver spider’s invasion is one example of the path that another species could take, likely causing damage to the environment.
A large, colorful invasive species called orb-weaver spiders is spreading across the U.S. Populations have been growing in parts of the South and East Coasts for years, and many researchers believe it’s only a matter of time before they spread across much of the continental United States.
But spider experts say there’s no need to worry too much.
“My sense is that people love strange, bizarre and potentially dangerous things,” said David Nelsen, a biology professor at Southern Adventist University who has studied the orb-weaver spider’s range expansion. “This is the kind of thing that ticks all the boxes for mass hysteria.”
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Instead, scientists are concerned about the rise of invasive species that can harm crops and trees, a problem exacerbated by global trade and climate change, which are making local environmental conditions more hospitable to pests that previously couldn’t survive frigid winters.
“I think it’s a canary in the coal mine type of species, because it’s so conspicuous that it attracts attention,” says Hannah Burlack, professor and head of the entomology department at Michigan State University. But the shy creatures pose little danger to humans; instead, invasive pests like fruit flies and wood borers are more damaging, Burlack says.
“This is a global concern because it makes it harder to manage all the activities we do, including environmental protection, agricultural production and human health,” she said.
A giant spider native to East Asia, the Oriental Golden Thrush, was spotted in Johns Creek, Georgia, on October 24, 2021. Populations of this species have been growing in parts of the South and East Coast in recent years, and many researchers believe it’s only a matter of time before it spreads across much of the continental United States. (AP Photo/Alex Sands, File)
What is a Joro Spider?
The Jorog spider belongs to a group of spiders called orb-web spiders, named for the wheel-shaped webs they build. Native to East Asia, they are vibrant yellow and black in color and can grow up to three inches long with their legs fully extended.
But they’re pretty hard to spot this time of year because they’re still early in their life cycle and are only about the size of a grain of rice. A trained eye can spot them spinning softball-sized nests on front porches or thin threads of golden silk covering grass patches. Adults are most commonly seen in August and September.
Where are they heading?
Scientists are still trying to figure out why, said David Coyle, an assistant professor at Clemson University who worked with Nelsen on a study of the gnat’s range published last November. The gnat’s core population is mainly in Atlanta, but it spreads into the Carolinas and southeastern Tennessee. In the past two years, a satellite population has become established in Baltimore, Coyle said.
So when will the study result lead to the species becoming more prevalent in the Northeast? “It could be this year, it could be 10 years from now. We really don’t know,” he said. “We probably won’t get there in a year. We need to take incremental steps.”
Can they fly?
The larvae can — using a tactic known as “ballooning” — allow young spiders to use their webs to harness the Earth’s winds and electromagnetic currents to travel relatively long distances, but fully grown spiders have never been seen taking flight.
What do they eat?
The spiders eat whatever falls into their webs, mostly insects, which means they may compete with native spiders for food, but that may not be all bad: The spiders they catch each day also become food for native birds, as personally documented by University of Georgia researcher Andy Davis.
Some observers have hoped that the spiders might gobble down invasive red spider mites, which are devastating trees on the East Coast, but Coyle said “they might eat a few, but it’s not going to have any impact on the population.”
Are they dangerous to humans?
Nelsen said that while the spider, like other spiders, is venomous, it’s not deadly to humans and doesn’t pose any medical problems — at worst, a spider’s bite can cause itching and an allergic reaction — but the timid creatures tend not to bother humans.
What could one day really hurt humanity is a widespread invasion of the green stink bug or other organisms like the star fly, a type of fruit fly, that threaten the natural resources we depend on.
“I try to remain scientifically objective, which is probably my way of insulating myself from the sadness of it all, but there’s a lot of damage being done to ecosystems all over the world for a lot of reasons, mostly because of humans,” Davis said. “To me, this is just another example of the impact that humanity has on the environment.”
