Giant Joro Spider In MD: Residents Urged To Report Sightings

A professor at a Maryland university is asking the public to help track the movements of the giant Joro spider, a Post-It Note-sized, flying arachnid that has burgeoned in the southern United States and is slowly moving north.

Angela Chuang, an assistant professor of environmental science and biology at Washington College, issued the call to action for residents in the Baltimore area and on Maryland's Eastern Shore, according to a statement. Chuang is currently the only researcher studying the Joro spider's population in the Northeast, which was first documented near Elkridge in 2022.

Since then, Joro spiders have been reported in both Howard and Anne Arundel counties, according to JoroWatch.org. A map provided by Chuang also shows a reported sighting in Baltimore County.

According to Chuang, the Joro spider is large and can sometimes be confused with yellow garden spiders because of their similar size and coloring. Yellow garden spiders are native to Maryland.

“The main thing is, we would like it if people could report when they see these spiders, so we have a better understanding of how Jorō spiders are spreading around, especially because this is a distinct population from the older one,” Chuang said. “It represents an opportunity to study an invasive population at its earliest stages.”

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What is the Joro spider?

The Joro spider is an orb-weaver, named for their wheel-shaped web. Females are brightly colored with red, blue and yellow hues while males are brown. Both can grow as long as three inches when their legs are fully extended.

Adult Joros are most commonly seen in August and September.

Baby Joros uses a tactic called "ballooning" to travel, meaning they use their webs to harness the winds and electromagnetic currents to travel long distances. If northern winds and spiderling births align, it could mean Joro spiders will spread to more northerly states as soon as next summer.

Where is the Joro headed?

Scientists are still trying to figure that out, but it's "only a matter of time" before Joro spiders head to states as far north as New York and New Jersey, University of Georgia research scientist Andy Davis told The New York Times in 2023.

The Mid-Atlantic states would make sense as the next destination for the spiders, as the region is at the same latitude as places in Asia where they thrive. The species can survive a brief freeze that kills off other spiders and has about double the metabolism of its relatives, according to one study.

“New York is right in the middle of where they like to be,” Davis told the Times.

Currently, their central population is primarily in Atlanta, but it has expanded to the Carolinas, southeastern Tennessee and parts of eastern Alabama, according to JoroWatch.org. In September 2025, a sighting was reported as far north as Bucks County, Pennsylvania.

Are Joro spiders dangerous?

The Jorō spider may look imposing, but Chuang’s prior research, conducted while she was a postdoctoral researcher at Clemson University, found that the species is not considered a health or safety threat to humans or pets.

In an interview with Clemson about her work, Chuang said that no danger was found, and even when bitten, subjects had little to no reaction to bites.

“We hope these studies teach people some of the dos and don’ts around managing these spiders and go a long way towards alleviating any personal safety and health concerns around them,” she said.

Chuang said her chief concern remains the Joro spider’s effect on local wildlife.

“I am very interested in studying this new local population to determine if Jorō spiders are having a negative impact on native spider communities," she said. "We have observed them quickly becoming the most numerous spider species within a few short years of them arriving to new sites, which is characteristic of other invasive species.”

What do Joros eat?

Joro spiders will eat whatever lands in their web, usually insects. While that means they could compete with native spiders for food, Mike Raupp, professor emeritus of entomology at the University of Maryland, told WTOP that their diet could be a benefit to area residents.

“They trap many, many invasive pests, including things like spotted lanternflies and brown marmorated stink bugs, which they love to eat,” Raupp said.

How do I report a Joro spider sighting?

Chuang said residents should photograph and report sightings using the popular iNaturalist app to understand how quickly and broadly the species is spreading in the Mid-Atlantic.