The invasive joro spider was first spotted in Pennsylvania.
Six of the giant, colorful spiders, which were already spreading across northeastern states including New York and New Jersey, were spotted in the yard of a Bucks County home on Sept. 5, according to the interactive tracking system JoroWatch. A state entomologist then visited the site to confirm the location and identification.
The species, Trichonephila clavatais native to East Asia, mainly Japan. It grows up to 10 cm (4 in) with legs as long as 20 cm (8 in) and can spin large golden webs up to 3 m (10 ft) wide.
According to JoroWatch, females are recognizable by their yellow abdomen and broad blue-green bands on their backs, as well as yellow and red markings on their bellies. They also have long black legs often striped with yellow bands.
Males are smaller and mostly brown, with two long yellow stripes on each side of their abdomen and a dark brown stripe down the middle.
Joro spiders were first spotted in the United States in northern Georgia in 2014, though they likely arrived in shipping containers years before. According to a 2022 University of Georgia study, Joro spiders differ from the closely related golden silk spider in that they have twice the metabolic rate and a 77% higher heart rate.
Thus, unlike the golden silk spider, which moved to the southeastern United States from the tropics 160 years ago but was unable to spread due to its inability to withstand cold temperatures, the joro spider is able to survive freezing.
Despite their intimidating exterior, Joros are considered quite shy and harmless towards people and pets.
Last year, scientists at the University of Georgia compared the reactions of more than 450 spiders from 10 different species to a slight disturbance—a turkey baster that blew two puffs of air at the spiders. While most species froze for less than a minute before resuming their normal activities, joro spiders remained motionless for more than an hour.
“They actually go quiet and wait for the disturbance to go away,” Andy Davis, lead author of the study, told the university’s journal. “These spiders are actually more afraid of you than the other way around.”
