The invasive joro spider has been spotted for the first time in Pennsylvania.
Six of the giant, colorful spiders, which were already spreading across north-east states including New York and New Jersey, were seen in the yard of a home in Bucks county on 5 September, according to the interactive tracking system JoroWatch. A state entomologist then visited to confirm the location and identification.
The species, Trichonephila clavata, is native to east Asia, primarily Japan. It measures up to 4in (10cm) with legs as long as 8in (20cm), and can spin large, golden webs up to 10ft (3m) wide.
Females can be identified by their yellow abdomen and broad blue-green bands on their back, as well as yellow and red markings on their belly, according to JoroWatch. They also have long black legs that are often striped in yellow bands.
Males are smaller, and mostly brown, with two long yellow stripes on both sides of their abdomen and a dark brown stripe in the middle.
Joro spiders were first spotted in the US in north Georgia in 2014, though they probably arrived on shipping containers years before. According to a 2022 University of Georgia study, joro spiders differ from the golden silk spider, a close relative, as they have double the metabolism rate and a 77% higher heart rate.
As a result, unlike the golden silk spider – which moved to the US south-east from the tropics 160 years ago, but has been unable to spread due to its inability to withstand cold temperatures – the joro spider is able to survive freezes.
Despite their intimidating exterior, joros are considered fairly shy and harmless to people and pets.
Last year University of Georgia scientists compared the responses of more than 450 spiders across 10 different species to a mild disturbance – a turkey baster that blew two puffs of air onto the spiders. While most species froze for less than a minute before resuming their normal activities, the joro spiders remained still for more than an hour.
“They basically shut down and wait for the disturbance to go away,” the study’s lead author Andy Davis told the university newspaper. “These spiders are really more afraid of you than the reverse.”
