Jorō Spiders: Yellow and Blue-Black Shy Giants Spreading Across the US

If you live in the southeastern United States, you may have encountered a large spider with striking yellow and black stripes on its legs and body.

This is the Joro spider, a native of East Asia that was first reported in North America in 2014.

Despite its fearsome appearance and venomous bite, the Joro spider is harmless to humans and may even be beneficial to the local ecosystem.

What are Joro spiders?

(Photo : MARTIN BERNETTI/AFP via Getty Images)

Joro spiders belong to the genus Trichonephila, which includes several species of orb-weaving spiders that produce golden silk, as per Penn State University.

They are named after Jorōgumo, a mythical creature in Japanese folklore that can transform into a beautiful woman to lure unsuspecting men.

Joro spiders can grow up to three inches long, with females being much larger than males.

They have bulbous body with bright yellow stripes and red markings on the underside. They weave large webs that can span several meters and shine like gold in the sunlight.

Joro spiders are found throughout Japan (except Hokkaido), Korea, Taiwan, China, and parts of Southeast Asia.

They have recently expanded their range to the southeastern United States, where they have been reported in Georgia, South Carolina, North Carolina, Tennessee, Alabama, Maryland, Oklahoma, and West Virginia.

Scientists believe they may have been introduced accidentally through international trade or travel.

How do Joro spiders survive and spread?

Joro spiders are adaptable and resilient creatures that can survive in various habitats and climates.

They feed on insects and other small animals that get caught in their webs, as per Phys.org.

These arachnids mate in the fall and lay eggs that overwinter until spring, and they can disperse by ballooning, a process where they release silk threads that catch the wind and carry them to new locations.

A recent study by researchers from the University of Georgia and Clemson University found that Joro spiders have a higher probability of surviving a brief freeze than other closely related species of the same genus.

They also have a faster metabolism and heart rate when exposed to low temperatures.

These findings suggest that Joro spiders can tolerate colder climates than their tropical origins and may expand their range further north along the Eastern Seaboard.

Also Read: 7 Surprising Facts You Didn't Know About Sea Spiders

Are Joro spiders harmful or helpful?

Joro spiders are harmless to humans and pets, as their venom is not potent enough to cause serious harm.

Their fangs are usually too small to pierce human skin, and even if they do bite, the symptoms are mild and short-lived.

Joro spiders are also not aggressive or territorial, and will usually retreat or drop to the ground when disturbed.

These spiders may even be helpful to the local ecosystem, as they provide an additional food source for native predators such as birds.

They also prey on insects that may be pests or vectors of diseases. They do not seem to compete with or displace native spider species, as they occupy different niches and habitats.

Therefore, scientists advise people to learn to live with Joro spiders and appreciate their beauty and diversity.

They also encourage people to report any sightings of Joro spiders to citizen science platforms such as iNaturalist or SpiderWebWatch, which help researchers monitor their distribution and impact.

Related article: Carnivorous Garden Spiders Are Actually Omnivores, Researchers Find