Joro spiders made it to the US, but the panic is overblown.
Posted on Jun 7, 2024 10:00 AM EDT
A colorful adult female Joro spider. These arachnids are native to parts of Southeast Asia. Kimberly R Fleming/iNaturalist, CC BY-NC 4.0 license
Spotted lanternflies are so four years ago. The hottest new bug fad isn’t even the noisy cicadas currently buzzing all over the Midwest. It’s enormous, yellow, ‘flying’ Joro spiders. Multiple articles would have you believe that there is a serious threat to humans from hoards of spiders jumping out of thin air straight on our faces. However, while the size of these arachnids–particularly the females–can be a bit scary and creepy, their threat to humans is quite low. Here’s what you need to know.
What are Joro spiders?
Joro spiders (Trichonephila clavata) are a species of large orb-weaver spiders. They are native to Southeast Asia, but were accidentally introduced to North America via a container ship.
[Related: Spider glue might evolve faster than the spiders themselves.]
“They were first found in the United States in Georgia in 2014,” Penn State University entomologist Michael Skvarla tells Popular Science. “Since then, they have spread across much of northern Georgia and into adjacent parts of North and South Carolina.” They generally eat the small insects that get trapped in their webs–including the invasive, ravenous spotted lanternflies. These webs can also be up to 10 feet wide.
These bugs are pretty hard to miss. Adult females typically have bodies that are about one inch long, with legs that span up to four inches. The adult males are generally smaller and are more brown in color. “They’re big and colorful. The only other web-building spider of similar size in our area are golden silk orbweavers, which are native to the Southeast,” says Skvarla. “Golden silk orbweavers are a darker yellow brown color while Joro spiders are bright green and gray with black legs.”
Can they fly?
While they cannot really fly, some studies show that this genus is particularly good at “ballooning” or “parachuting.” Numerous arachnids can do this by shooting threads into the air that are still attached to their bodies. The wind then picks the bugs up and carries them to another spot, giving the illusion of flight. They can move tens to hundreds of miles with this process.
Are they poisonous?
They are not poisonous to humans and their fangs are not designed to puncture human skin. The venom that they do carry is weak and can only hurt the smaller insects that they eat.
[Related: Black widows battle their even deadlier cousins in a brutal spider war.]
“The spiders are reluctant biters that prefer to stay in their webs,” says Skvarla. “When bites happen because people intentionally handle Joro spiders, the venom is weak and bites are not even as painful as a bee sting.”
A 2023 study found that Joro spiders are some of the most shy spider species on the planet and prefer to just hunker down.
When will they arrive in the Northeast?
We don’t really know, but probably sometime this year. Joro spiders tolerate the cold, and have been slowly creeping further north. One 2023 study found that they were spreading faster to northern parts of the country than southern, spreading to the northeast the quickest.
How concerned should we be?
“Joro spiders aren’t a concern for people, so the risk is overhyped. Their impacts on the environment are unknown, but they seem to prefer urban areas, which are already highly developed and degraded,” says Skvarla. “My biggest concern is the impact they may have on native golden silk orb weavers, either through competition or hybridization.”
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