Joro spiders are bright yellow and black spiders known for their huge spiderwebs. This colorful species comes from East Asia, but Joro spiders have recently invaded warm American states like Georgia and South Carolina. Many people consider Joro spiders pests because of their large size and ability to bite humans. Here’s everything you need to know about Joro spider identification, health risks, removal, and more.
What Are Joro Spiders?
The Joro spider (Trichonephila clavata) is a member of the Araneidae family. This group includes golden orb weaver spiders. These species create elaborate spiderwebs where female spiders live. Male orb weaver spiders like the Joro travel by “ballooning.” During this process, they use strands of silk to catch an electrical current or the wind and drift to new locations.
Joro spider identification. You can easily identify the big and colorful Joro spider in its adult form. The female Joro spider has blue-black and yellow stripes on its back and legs. The spider’s underside has distinct red markings.
The Joro spider spins immense golden webs spanning over 3 feet (1 meter). They make their webs approximately 3 to 9 feet (1 to 3 meters) above the ground.
Adult females have a cylindrical abdomen and a round cephalothorax, or head. Their body can grow up to 1 inch long, and their leg span can measure up to 4 inches, which is roughly the size of a human palm. Females have tufts of golden hair on their legs.
Immature female spiders have a brown head, a narrower abdomen, and a blotchy black and yellow pattern on their back. As the spider ages, this pattern becomes distinctive black and yellow bands.
Male Joro spiders are much smaller than females, and you may only spot them when they’re perched on a female’s web. Their body length can measure up 0.3 inches, and they have drab brown bodies with darker stripes. Males only spin their own webs to catch prey as juveniles.
What do Joro spiders eat? Joro spiders hunt and eat other insects like grasshoppers and moths. They snare these insects in their huge webs and use their venomous bite to weaken them. This hunting style gave the spider its Japanese name, "jorō-gumo.” This name means “entangling or binding bride”.
In America, scientists have observed Joro spiders eating plant pests like adult brown marmorated stink bugs. These common pests are an invasive species that can damage plants and invade houses. Other local spiders don’t eat the stink bugs, so the Joro spiders may benefit the ecosystem by hunting them.
Joro spider life cycle. Joro spiders typically live up to 1 year in temperate areas. Adult females lay 1 to 5 egg sacs between September and November. Each egg sac contains approximately 400 to 500 eggs. The female attaches the sac to human-made structures, leaves, or tree bark.
Spiderlings hatch 5 to 7 months later. They create a communal web, molt, and balloon away to new locations. Many eggs and spiderlings don’t reach maturity because other spiderlings prey on them before dispersing.
Female Joro spiders reach adulthood in 3 to 5 months, but males mature earlier. Adult spiders of both sexes frequently live in the same spiderweb, along with kleptoparasites that steal their food.
All adult Joro spiders die in the winter.
Where Do Joro Spiders Live?
Where do Joro spiders come from? This species’ native range includes China, India, Japan, Korea, and Taiwan. In its natural habitat, the Joro spider typically lives in fields, forests, mountainsides, and human-made buildings near urban woods.
Joro spiders in America. The Joro spider was first detected in 2013 in Hoschton, Georgia. A shipping container likely transported the invasive species from China or Japan. Since its arrival, the spider has spread through the southeast in Georgia, South Carolina, and other states.
Experts report that Joro spiders tolerate cold weather well, which means the species may spread to northeastern states in the future.
Signs You Have Joro Spiders
You can easily determine that you have Joro spiders if you see the large, striped females in your home or yard. You may also spot their enormous spiderwebs around your house. Potential Joro web locations include home exteriors near porch lights, shrubs, small trees, tall weeds, vinyl siding, and wooden decks.
Why Do You Get Joro Spiders?
Joro spiders often live around buildings and houses near small urban woods. You’re more likely to see this species if human activity has disturbed their habitat.
These spiders rarely enter buildings and homes. But outdoor firewood and landscaping can harbor Joro spiders, so moving these items away from your house is a good idea.
Health Risks of Joro Spiders
Despite their frightening appearance, Joro spiders present little threat to humans and pets.
Do Joro spiders bite? The Joro spider can bite humans, but it prefers to avoid confrontation. The spider also has small fangs that don't easily pierce human skin. In the unlikely event that a Joro spider bites you, the bite will feel like a bee sting and may cause temporary redness.
Are Joro spiders poisonous? The Joro spider has venom that affects insects, but its bite won’t harm humans.
How to Treat Joro Spider Bites
A Joro spider bite typically doesn’t require medical intervention. The bite may cause a small amount of pain and redness, but these symptoms quickly disappear.
In rare cases, a person could have an allergic reaction to a Joro spider bite and need treatment from a healthcare provider. But no allergic reactions to this species have been reported yet.
How to Get Rid of Joro Spiders
If you have a Joro spider infestation, you can use several methods to remove them.
You can consistently destroy spiderwebs hanging from buildings and trees. The Joro spiders may choose to move to a new location.
A pest control professional can also help you remove Joro spiders and their webs.
Experts encourage you to leave Joro spiders alone if they’re not directly impacting you. You may accidentally damage the ecosystem or kill native insect species if you try to chemically remove or squish Joro spiders. This species won’t harm humans or pets, so it’s best to admire it from a distance.