They are huge, have eight blue-black and yellow striped legs, and may soon be moving across much of the eastern seaboard of the United States.
A study published in the journal Physiological Entomology indicates that the palm-sized joro spider, which has been largely confined to warmer southeastern states for nearly a decade, may soon colonize regions with warmer climates. cold.
That’s because researchers have found that large arachnids have a higher probability of surviving a brief freeze than other closely related species in the same genus.
“People should try to learn to live with them,” Andy Davis, a researcher at the Odum School of Ecology and one of the authors of the recent study, told UGA Today, a publication of the University of Georgia.
A joro spider can grow to about 3 inches in length, including a large bulbous body with bright yellow stripes. Its underbelly has distinctive red markings and it spins large webs that appear to have been woven from golden silk.
It is named after Jorōgumo, who in Japanese folklore can transform into a beautiful woman to prey on unsuspecting men.
Despite their startling appearance — and their namesake — Davis noted that the joros don’t appear to be harmful or have much of an effect on local agriculture or ecosystems. In fact, he said, they can benefit native predatory birds as a supplemental food source. And, while they kill their prey using venom, scientists say they are harmless to humans and pets because their fangs are usually too small to break through human skin.
In other words, try to leave them alone, Davis says.
“If they’re literally in your way, I might consider removing a canvas and moving them to the side, but they’ll be back next year,” Davis added.
To learn more about their biology, the researchers compared joros to golden silk spiders, a closely related species native to tropical climates in Southeast Asia and established in that same region of the United States in over the past 160 years.
They found that joro spiders have twice the metabolism of their spider cousin and a 77% faster heart rate when exposed to low temperatures.
“These results suggest that the jorō spider may exist in a cooler climatic region than the southeastern United States,” the study states.
Another reason they seem to spread so quickly is that they are good travelers. Newborn babies do what is called ballooning, which is when they use webbing bristles to carry them in the wind to new places.
There’s also the human factor, said Benjamin Frick, an undergraduate researcher on the project.
“The potential for these spiders to spread through the movement of people is very high,” Frick said.
He added, “Anecdotally, just prior to publishing this study, we received a report from a UGA graduate student who had accidentally transported one of them to Oklahoma.”
Joro spiders are native to Japan and likely made their way to the United States in shipping containers, researchers say.