Timothy Best, MSPH, BCE
Technical Manager, Terminix
Updated on: September 14, 2022
Some of the biggest news on the “web" these days is being made by a spider. If you're reading this, it's likely that you've already started your own research on the invasive Joro spider, Trichonephila clavata.
This spider has been making the news in the pest industry as a result of recently published research that suggests, due to the invasive spider's physiology, it has the potential to increase its range by being able to survive in cooler climates. This study has resulted in some media coverage prompting a new level of arachnophobia and fear.
Let's separate fact from fiction and understand what this research is saying, as well as what it means for you and your neighborhood. We'll answer some of the most commonly asked questions about this spider, including:
- What is a Joro spider?
- What does a Joro spider look like?
- Are Joro spiders poisonous?
- Joro spider origins and habitats
- Joro spider lifespan
- What do Joro spiders eat?
- What eats the Joro spider?
- Joro spider web strength and applications
- Are joro spiders a threat to native ecology?
- How are Joro spiders moving about the United States?
- Is control of the Joro spider necessary?
- Don't panic about the Joro spider?
- Joro spider prevention tips
What is a Joro spider?
Joro spiders are an invasive species of Golden orb weaver spider that were first discovered in North Georgia in 2014.
How Joro spiders arrived in the United States is not fully known, but it's assumed their introduction was accidental through commerce and through hitchhiking in shipping containers from overseas.
Since their discovery in the U.S. in 2014, the Joro spider has increased its range to areas in Alabama, North Carolina, South Carolina and Tennessee.
What does a Joro spider look like?
The key characteristics of a Joro spider are:
- Extremely long legs (legs can be four times as long as the body)
- Striped legs (often yellow and black)
- Bright colors (red, yellow, brown, blue, black)
- Usually appear in fall months (September and October)
- Weave distinct three-layered, orb-shaped, gold-tinted webs
The adult female Joro spider is large and brilliantly colored with bright yellow and grey-blue bands and patterns on both its upper and lower abdomen. The cephalothorax is covered with silvery and golden hairs, and the legs are black with yellow bands.
Maybe the most stunning feature of this spider is its size. Female body length can measure up to 1 inch, with a leg span of up to 4 inches. To put that into perspective, the average size of a human palm is 3.1 to 3.5 inches.
Females lay eggs in the fall. There can be up to 1,500 eggs in a thick-walled sac that's covered in bright yellow silk. Baby Joro spiders hatch in the spring and look like smaller versions of their adult counterparts.
Male Joro spiders are much smaller and not as vibrantly colored when compared to females. Their body length is typically 0.3 inches, with more dark brown colors.
Are Joro spiders poisonous?
Joro spiders are poisonous, but do not pose a danger to humans as they are typically reluctant to bite and their venom is very weak. The fangs of a Joro spider are essentially incapable of piercing or breaking human skin. Joro spiders will often only attempt to bite if they are being constrained. Science tells us that the Joro spider is not considered to be dangerous. In fact, these spiders are considered merely a nuisance to humans.
Are Joro spiders harmful to your pets? Again, Joro spider poison is extremely weak. If somehow the spider manages to puncture your pet's skin (which is unlikely), the animal may have an allergic reaction. Ingesting a Joro spider could cause an upset stomach.
Joro spider origins and habitats
Named after a Japanese spider demon (Jorogumo), Joro spiders hail from Southeast Asia. They are common in China, Japan, Korea, Taiwan, and Vietnam. Back in the early 2010s, the spider somehow arrived in Georgia, likely via shipping containers imported into the US. Since then, these arachnids have been spotted in various points across the southeast.
While Joro spiders prefer warmth and humidity, they can survive in virtually any weather. Recent research indicates they may be able to survive in much colder temperatures than originally known. Their resistance to the cold could cause them to spread to the colder states in the future.
Joro spider lifespan
The Joro spider's lifespan is typically around 12 months. An adult female spider lays its eggs in the fall. One egg sac can contain between 400 and 1,500 eggs. Baby Joro spiders hatch in the spring or early summer.
It takes around two to three months for spiderlings to reach sexual maturity. Before then, these pests are mostly unnoticeable to humans. Baby Joro spiders can transport themselves through ballooning. They release silk, stay attached to it, and let the wind carry them to their next destination. Ballooning allows Joro spiderlings to travel up to hundreds of miles.
What do Joro spiders eat?
A Joro spider's diet includes a variety of insects, such as mosquitos, stink bugs, yellow jackets and biting flies. They wait until a small insect gets tangled in their web. Once it's inside, the spider wraps the prey in silk and uses venom to subdue it.
What eats the Joro spider?
Joro spiders are typically food for birds and other predators that eat spiders and insects. Since these spiders are fairly new to the US, their role and impact on the ecosystem remains unclear.
Joro spider web strength and applications
Joro spiders weave strong, three-layered webs that can be up to 10 feet wide. A research team at Shinshu University in Japan used genes of Joro spiders in silkworms in order to develop durable spider silk.
This new, high-tensile fiber can have many uses. For example, it's great for making stockings and socks, as well as fishing line and tennis racket netting.
Are Joro spiders a threat to native ecology?
As with most invasive, non-native species, there is a lot we don't yet know or understand about the Joro spider. Their impact on native species and environments is not clear right now, but many researchers believe their presence will not be threatening.
How are Joro spiders moving about the United States?
Joro spiders use two primary methods to move around. One method is by hitchhiking with humans – winding up in cargo shipped around the world and finding their way to new lands. The other method is through a process known as ballooning.
Ballooning is when newly hatched spiderlings climb as high as they can, stand on raised legs and then release several threads of silk from their spinnerets. These thin silk threads act as a parachute of sorts. As they're being swept up in air currents, the spiderlings will travel with the wind.
Depending on species and other environmental factors (like wind speeds), ballooning may carry spiderlings from tens to hundreds of miles away. Current estimates only have the Joro spider being moved into bordering states no more than 80 miles away from where it was originally found. That's roughly about 8-10 miles per year so far.
Is control of the Joro spider necessary?
Due to their lack of medical and economic impact, control measures haven't been necessary or established for Joro spiders. The Joro spider is a nuisance pest and doesn't present enough of a threat to require pesticide applications.
If Joro spiders and their webs are found on or around a structure, they can be removed with a broom or a cobweb removal brush.
Don't panic about the Joro spider
This new Joro spider research suggests that the Joro spider can exist in colder climates outside of the southeastern United States, but does not imply they'll soon be dropping from the sky in masses into backyards across the country. While there's potential for the Joro spider to move to and survive in cooler climates, there's no data to support that they will spread quickly.
Joro spider prevention tips
While Joro spiders aren't dangerous to humans, they can be a serious nuisance. If you want to prevent these pests from settling in your yard or around the house, consider these prevention tips:
- Watch your landscaping. Rich vegetation against your house could cause Joro spiders to settle there.
- Don't leave outdoor lights on. Bright lights can attract insects, which in turn can attract Joro spiders that will eat them.
- Eliminate hiding places. Joro spiders prefer lush vegetation, leaf piles, and woodpiles.
- Clean your home regularly to check for spider webs and remove them.
- Seal cracks and holes around windows and doors to prevent spiders from entering.
If prevention methods don't work, and you find Joro spiders in your yard, consider contacting a pest control specialist.