Is the Invasive Joro Spider Headed to a Town Near You?

The invasive Joro spider (Trichonephila clavata) is endemic to East Asia. It was first discovered in the U.S. in North Georgia in 2014, and the spiders have returned to the Georgia area each summer. Experts believe they came to the United States via shipping container several years before. Each year, their populations have continued to grow, with experts noting significant increases in recent summers.

Georgia residents have reported widespread sightings of Joro spiders in their backyards. However, Joro spiders are not just in Georgia’s residential areas. They are also beginning to make their homes across the South, leading many to wonder: where will Joro spiders go next?

What Are Joro Spiders?

Joro spiders are an invasive species from East Asia. These spiders are a type of orb-weaver, which spin circular, wheel-shaped webs. They have brilliant yellow and black markings on their bodies and black legs with yellow bands. The females, which are about twice the size of males, also have blue stripes and red patches on their bodies. With their legs extended, the Joro spider can reach up to 3 inches across, with bodies about 1.5 inches long.

Their webs can be upwards of six feet wide, and they are said to appear gold in the sunlight. These webs are also very strong, capable of holding 2.5 ounces. This is strong enough to support many common birds or even bats.

Like all spiders, Joro spiders are venomous, but this is generally only a concern for their prey. A bite immobilizes any insects that become ensnared in their web. However, they pose no threat to humans or pets. Like most creatures, they might bite to defend themselves if they feel threatened, but a Joro spider bite likely won’t even break the skin. Scientists who study the spiders say a bite might itch or cause a mild allergic reaction.

The Joro Spider’s Impact

Invasive species typically pose a threat to local ecological systems. There are concerns that the Joro spider may outcompete naive spiders. Researchers have observed reduced native spider populations in areas with large Joro spider populations. However, Joro spiders may also do some good. Georgia entomologists say that the population of Joro spiders may be the natural answer to battles against other pests.

Another invasive species, brown marmorated stink bugs, are known for destroying Georgia crops. Historically, they have never had a natural predator — until now. Joro spiders could also lower populations of mosquitoes and other biting flies. Their webs can also provide a food source for birds, or even other spiders. Biologists are currently studying the spiders to determine their ecological impact.

Where Is the Joro Spider Going Next?

The next big question about Joro spiders is: where are they headed? Although their primary population is centered in Georgia, researchers believe they have expanded to North and South Carolina, Tennessee, and Alabama. Some scientists have also observed populations in Pennsylvania, Oklahoma, West Virginia, and Maryland. Scientific modeling suggests that they would be able to survive environmental conditions throughout most of eastern North America.

Although the Joro spiders alive today will die by the end of November, their offspring could begin to travel across the South and the Northeast by next summer. Joro spider egg sacs are spun from a light silk and usually contain around 400 hatchlings.

Next spring, those hatchlings will emerge. Then, they will use a string of silk to ride the wind to their next destination. These hatchlings can cross long distances using this method, which is called “ballooning.” Next summer, many other southern American cities may see Joro spider webs as the spiders begin to pop up. As the cycle continues, Joro spiders could make their way across the United States as their hatchlings ride the winds further each spring.