The large, scary-looking Joro spiders have spread from Asia to the southern United States and are now poised to colonize the country’s colder climates, but they are nothing to fear and could end up helping local ecosystems.
This is according to scientists who have studied arachnid invaders since they first arrived in Georgia around 2013.
In just a few years, the golden webs woven by bright yellow, dark blue, and red spiders have become a common sight across the state, and new research suggests they will scramble up the east coast later.
“The reason we got involved in this project is that they literally fell into our wombs,” Andy Davis, an ecologist at the University of Georgia, told AFP on Friday.
“They’re all over here in North Georgia, they’re all over my yard.”
Davis began studying the new resident, comparing it to the golden silk spider, which arrived in the southeastern United States about 160 years ago from the tropics.
Writing in an article published in the journal Physiological Entomology, he and his co-author Ben Frick found similarities but also notable differences between relatives.
The Joro spider’s metabolic rate is about double that of its cousin, its heart beats 77% faster, and it can survive short frosts. They also grow faster.
Together, these traits mean it can survive colder climates better, which isn’t entirely surprising given that it’s native to temperate Japan.
They are also adept at gliding – webs that act like parachutes and catch air currents – allowing them to fly up to 100 miles (160 kilometers).
The paper examined the records of iNaturalist, which tracks animal sightings, and found that the spider’s range had already spread far beyond Georgia to include neighboring states of South Carolina, North Carolina, and Tennessee.
There was also a report from distant Oklahoma.
Left to fend for themselves, Joros would likely go up the coast in 20 years, but it will likely happen faster if they hitchhike the vehicles, Davis said.
– Ask for clemency –
This is probably how they got to the United States in the first place: either a clandestine female spawned when she landed on a ship, or an egg sac was brought in and hatched in the spring.
Invasive species are often linked to destruction, such as the spotted lantern, native to Southeast Asia which arrived in the US state of Pennsylvania in 2014 and is known to decimate fruit trees and ornamental plants.
But the Joros’ explosive numbers aren’t necessarily a cause for concern, Davis said.
“The golden silk spider is everywhere in the southeast and it’s not causing any harm. It’s been here for so long, it has integrated into the ecosystem and the Joro could follow the same trajectory,” he said.
In fact, it could provide a hearty meal for native predators, such as mud dauber wasps, which hunt spiders. Other beneficiaries could include local lizards.
Another plus: Joros also feed on insects that local spiders don’t eat, such as the adult brown marble bug.
They are also not aggressive towards humans, nor are their fangs large enough to pose any kind of threat, Davis pointed out, who asked for leniency and understanding, not stigma.
“I don’t really think the Joros deserve to be crushed or killed like the spotted lantern – they’re not really out to get us and it’s not even their fault they’re here. They literally agreed to the trip,” he said.