Giant Joro Spider Arrives In MD: What To Know If You Spot One

MARYLAND — The Joro spider, a Post-It Note-sized arachnid that has burgeoned in southern U.S. states since 2021, has made headlines this week as some wonder when the wind-riding insect will arrive in their states.

In Maryland, the Joro spider is already here, according to experts and a website tracking the arachnid's movements.

The invasive species, which is native to East Asia, made its debut in Maryland last summer when populations were found in Howard and Anne Arundel counties.

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What is the Joro spider?

The Joro spider is an orb-weaver, named for their wheel-shaped webs. 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.

Joros are hard to spot at this time of year because they’re still early in their life cycle — they're only about the size of a grain of rice. Adults 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 this summer.

Where is the Joro headed?

Scientists are still trying to figure out 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 last year.

The Mid-Atlantic states would make sense as the next destination for the spiders as the region is 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 and southeastern Tennessee.

Are Joro spiders dangerous?

While the Joro is venomous, its venom does not pose a danger to humans or pets.

"You definitely do not need to run to the hills in fear of the Joro spider,” Mike Raupp, professor emeritus of entomology at the University of Maryland, told WTOP. When the Joro was discovered in Maryland last year, "Nobody was bitten, nobody died," Raupp said.

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, Raupp told WTOP that their diet could be a benefit to area residents.

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

The Associated Press and Patch editor Nicole Rosenthal contributed to this report.