Venomous Invasive Spider’s First Sighting in Massachusetts

Huge venomous Joro spiders have invaded yet another state, having been spotted in Massachusetts for the very first time.
The enormous black and yellow arachnid was noticed hanging out on its web by a resident of Boston’s Beacon Hill neighborhood, CBS reports.
This comes only months after ecologists warned that these spiders were likely to start moving into northeastern states.
Joro spiders (Trichonephila clavata) are native to East Asia, and were first noticed in Georgia in the early 2010s, and are believed to have been accidentally introduced to the U.S., likely through shipping containers or goods. In the years since, they have been spotted in Florida, Alabama, Mississippi, the Carolinas, Tennessee, Kentucky, Virginia, West Virginia, Maryland, Ohio, and now also Massachusetts, and are expected to invade even more states in the coming years.
“Organisms will spread to any environment to which they can tolerate (survive) and travel (disperse). The Joro spider is native to regions of Asia that get very cold, such as Korea and Japan,” David Nelsen, a Joro spider expert and professor at Southern Adventist University, told Newsweek. “These spiders die each winter, and their eggs are protected in a silk egg case. The eggs in these silk cases can survive/resist prolonged exposure to freezing temperatures. Then, when the weather warms up again, the next generation hatches and leaves the protective egg sac to disperse again,”
Females are much larger than males, with a body size of about an inch across, with long spindly legs that can span up to 4 inches. They are venomous, but this venom is not harmful to humans, and they tend to avoid interaction with us if possible.
“Joro spiders are not medically relevant, and their venom is not strong enough to produce more of a minor irritation in most people. So yes, they’re venomous, but they are not dangerous to people or pets,” David Coyle, an associate professor in the Department of Forestry and Environmental Conservation at Clemson University, told Newsweek.
This spider is known for its impressive “ballooning,” whereby they release silk threads into the air that act like parachutes, allowing them to “fly” short distances.
“When the spider is very tiny, it will climb to an exposed surface like the tip of a leaf or a fence, releasing a special silk that they use to ride the Earth’s electric fields and the wind,” Nelsen said.
“Most spiders probably won’t travel that far, but if they get caught in a strong wind, like during a storm, then they can disperse over huge distances, colonizing islands and, in our case, from further south to Massachusetts. So, while it is true that Joros can fly, they only do so when they are tiny (~ 1mm in total body length), not the large females you see in pictures or on the news. Don’t worry about a giant spider dropping from the sky; that won’t happen,” he assured.
These spiders are expected to pop up across more northern states in the coming years. Andy Davis, a researcher at the University of Georgia, suggested that they may be traveling to new locations by hitchhiking on people’s vehicles.
“They are likely to eventually expand throughout much of eastern North America,” Coyle said.
Because Joro spiders are relatively new to the U.S., the long-term ecological impact remains unclear. So far, research has found that they do compete with native spiders for resources such as food and space.
“Despite the nascence of T. clavata’s invasion, we have already found evidence of native spider biodiversity declines associated with its presence,” Nelsen and Coyle wrote in a 2023 paper in the journal Ecology and Evolution.
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Nelsen, D. R., Corbit, A. G., Chuang, A., Deitsch, J. F., Sitvarin, M. I., & Coyle, D. R. (2023). Veni, vidi, vici? Future spread and ecological impacts of a rapidly expanding invasive predator population. Ecology and Evolution, 13(11). https://doi.org/10.1002/ece3.10728