With their bright yellow bodies and distinctive multi-layered webs, it’s hard to miss them while walking along trails in Northeast Georgia or even lounging on a back porch.
The invasive species — which are native to China, Korea, Japan and Taiwan — started popping up in Northeast Georgia in 2014, according to Mattias Johansson, assistant professor of biology at the University of North Georgia Gainesville campus.
Like many others in Hall County, Johansson said the Joro spider caught his attention when it began appearing locally. The professor, who specializes in invasive species research, gathered a team of UNG students in August 2019 to begin measuring the arachnids’ potential ecological impact.
Although the pandemic threw a hiccup in the operation, Johansson said they have picked up their work this fall semester, focusing mainly on Joro spiders' prey.
How invasive are Joro spiders?
Over the past year, he said they have uncovered a few unknowns about the arachnid, including how it’s affecting native wildlife.
“One thing we’ve noticed is that they are probably competing for space with normal spiders,” Johansson said. “People have commented that there seems to be fewer writing spiders.”
Johansson said his team has found that certain predators do feed on the invasive species, including birds and mud dauber wasps. He said mud daubers will sting medium sized Joro spiders and use them to feed their larvae. Once the larvae break out of their eggs, they eat the arachnid alive.
“They have been found in (mud daubers’) nests,” he said. “I didn’t know mud daubers were generalists.”
By collecting samples of Joro spiders with his students and monitoring iNaturalist — a database for reporting wildlife sightings — Johansson said he doesn’t think their densities have increased in Northeast Georgia, nor does he have a true sense of their range.
One thing is for certain, spreading comes naturally to Joro spiders. Johansson said they use a ballooning technique, in which the spiders spin a web to catch the air current, allowing them to fly for 50-100 miles before latching onto a tree.
“If people are living out in Dawsonville and seeing them, they’re clearly spreading,” he said. “Individuals have gotten quite far. There was a report from North Carolina.”
Because of their size, Johansson said his research team knows the species must eat a lot to survive.
Gabby Lupica, a senior at UNG, said she started collecting prey remains from Joro spiders’ webs a week ago. Later in the semester, she will conduct DNA sequencing on the samples to determine what the arachnids are targeting for food.
“We’re basically seeing if they’re harming one indigenous species,” Lupica said. “They eat the prey, spit the carcasses out and they dangle in the lower webs. I go collect them and put them in a jar of ethanol.”
A place to call home
Now that it’s fall, Joro spiders are becoming easier to spot because they’re reaching the end of their year-long lifespans. Like most spider species, the females are significantly larger than the males, flaunting bright yellow hues and a splash of red on their abdomens.
Not to be confused with the writing and banana spider, Joro spiders stand apart by their larger size and distinctive, gold-tinted multi-layered webs. The females, including their leg span, can reach up to 3 to 4 inches.
The arachnids tend to live on the edge of woods, but Johansson said more people are noticing them around their homes, congregating in groups.
“Some have seen a giant web with half a dozen females,” he said. “It’s not natural circumstances. I can see why people find it off-putting.
Johansson said he suspects the spiders are tolerating living in close quarters because of prey availability. For example, they could live near an apartment’s hallway light because it draws in higher quantities of appetizing insects.
With their long-banded legs and large abdomens, Joro spiders may seem intimidating, but Johansson assures people they’re not dangerous. Like all spiders, they’re venomous, with a bite one could compare to a bee sting. However, unless a person is allergic to Joro spiders, Johansson said they shouldn’t be concerned.
“They’re pretty pacifistic,” he said. “They’ll most likely flee if you bother them. They’re not aggressive at all.”
Squashing Joro spiders may feel like a good deed, but it won’t have a significant effect on their population, Johansson said.
“There’s enough of them around, they can’t possibly be eradicated,” he said. “There’s going to be enough at the end of the day. They’re here to stay as far as I can tell.”