Joro spiders are the size of your palm. They weave webs up to three feet in diameter, and over the past decade, East Asian arachnids have spread throughout the southeastern United States.
“If you’re an arachnophobe, they’re the stuff of your nightmares,” said Andy Davis, a biologist at the University of Georgia who studies them.
But, Dr. Davis said, joros are “gentle giants” who are prone to shyness and are more prone to freezing than fighting. The results of his latest experiments, published this week in the journal Arthropods, show that spiders stay motionless for more than an hour when inflated with air from a turkey baster. In comparison, the small spiders seemed relatively unfazed, indicating that even large scary spiders can be scary cats.
The Joros were first spotted in northeast Georgia in 2013; Dr. Davis’ best guess is that the spider eggs arrived in shipping containers, as they tended to appear around highways. He first spotted a Joro spider while walking with his wife on his college campus; he remembers stopping to take a picture because “it was so striking”. Since then, he has been studying spiders.
Joros has been the subject of media attention as it spread; Dr. Davis suspects they will reach New York this summer. But unlike another invasive insect, the tree-destroying spotted lantern flies, which have a Death warrant in the Big Apple, there is no evidence that the joros affect the North American continent for better or for worse. (At the very least, their venom is too weak to harm humans.)
Despite the lack of data on their behavior, Dr. Davis said, the joros have a bad reputation because some people equate the spread of spiders in the South with boldness.
“People think the joros are in aggressive competition with the native spiders,” he said. The aim of the study, he added, is to assess “how aggressive are these joros?”
Dr. Davis and Amitesh Anerao, who recently completed their undergraduate studies in Georgia, set out to examine the boldness of spiders with a proven lab test: inflating the joros with the air of a turkey baster, then measure the time it took for them to resume movement. The experiment is based on the idea that cornered spiders can freeze in a last ditch attempt to avoid being snatched away by a hungry bird. The puff of air attempts to simulate the flapping of the bird’s wings.
When the researchers blew air on small garden spiders and orb weavers and extracted data from previous research on five other species, they found that it took an average of a minute and a half for the smaller spiders resume their movement.
The joros were another story.
“At first I tried to make them in the lab, but I mean some of the joros were freezing for more than two hours straight. By then the building was closing, I had to leave,” said Mr Anerao said, so he brought the spiders home to his apartment, where he could let the spiders take their time.
The joros in the study lasted on average more than an hour of immobility after being blown. The same goes for the golden orb weavers, a cousin of the joro and native to the Americas. The researchers say this behavior indicates that their genus, Trichonephila, is among the shyest spiders ever documented.
Angela Chuang, a postdoctoral researcher at the University of Florida who was not involved in the study, notes that aggression, in terms of fighting with other creatures, is different from boldness or lack of shyness.
They urged caution in extrapolating the overall behavior of spiders in the wild from their reactions in this study.
“I would be very careful to just call them shy spiders – like, yeah, in what context?” said Dr. Chuang. “Apparently they are shy in the context of being puffed up, which tells us nothing about their actual interactions with other species.”
Dr. Davis and Dr. Chuang agree that more experiments and observations are needed to understand how the joros interact with their new home. The results of another series of unpublished experiments offer a preliminary indication. Mr. Anerao put joro spiders in a container with native spiders “and had them fight to see who would win, and the joros always lost,” Dr. Davis said. “They were always the first to flee.”
If you spot a joro, rather than running away or running over it, Dr. Chuang offered to take a photo and upload it to a website like iNaturalist to help researchers track arachnids.
“Our research has been greatly aided by public awareness,” they said.