As soon as the black and yellow Jorō spider was first spotted in Georgia and the Southeast around 2013, experts were concerned that the invasive spider native to East Asia would do what is often feared of intruders that get too comfortable in their new habitat: feasting on local spiders’ preferred prey or even native and already threatened spiders themselves.
When scientists from the University of Georgia (UGA) set out to study Jorō spiders’ stomach contents, they were positively surprised. As described in their paper, published in PLOS One, Jorōs seem to have a different prey preference than most local spiders, with a taste for bugs we often consider pests. Overall, the findings show the eye-catching new arrivals seem to peacefully coexist with other arachnids, with experts urging people to lay low on insecticides.
“In trying to kill the spiders,” explained study co-author Jason Schmidt, professor of entomology at UGA, in a press release, “you’ll increase the likelihood of having a bunch of really difficult pests show up.”
Spider’s Stomach Content Reveals They Prefer Pesty Bugs
To better map what Jorō spiders (Trichonephila clavate) feast on away from their homes in Japan, China, Korea, and Taiwan, the research team studied the stomach content of over 200 individuals collected from 33 sites across Georgia and South Carolina. The scientists relied on DNA fragments found in Jorōs’ digestive system and compared them with those of over 140 local spiders to see how their diets matched.
Explore All OptionsAlthough there was some overlap, they found that Jorōs consumed 26 species local spiders would normally avoid. Also, with Jorōs present, native spiders seem to continue on their same diet, suggesting that Jorōs’ arrival doesn’t introduce noticeable competition for food, according to Schmidt.
Since Jorōs are known for their large, sticky webs, people were concerned they would pose another risk to the already threatened monarch butterflies. However, observations from the study couldn’t confirm that fear. On the contrary, the East Asian spider seems to be quite helpful.
“They’re feeding on things that we would consider pests,” said Schmidt. “A lot of little flies. For the size of the spider, it looks kind of like popcorn.”
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Ballooning to Their Next Destination
Jorō spiders are spreading rapidly across the state, in part because of a behavior called ballooning. As soon as the small spiders hatch in spring, they use their silk to catch a ride with the wind, a common tactic for spiders around the world.
Once they get to their new home, they get to work. Known for their “crazy-looking yellow webs that are often tangled with other webs,” as described by Schmidt, Jorōs build webs that are very distinct from other arachnids.
According to the researchers, Jorōs and local spiders are often observed living side by side, making it difficult to measure the newcomer’s impact on native spiders’ space.
“I don’t think they’re necessarily competing for space,” Schmidt said, “though others may have different opinions on that.”
Going Easy on the Pesticides
Considering the favorable climate of the region together with all their recent observations, the research team said Jorō spiders are likely here to stay. They’re also not picky with where they set up shop, as Jorōs have frequently been spotted near bustling roads and other human-made features.
Additionally, Jorō spiders are mostly harmless — for humans and our pets. Despite their intimidating coloring and 4-inch leg span, they tend to be very shy and avoid conflict.
“They’re pretty docile,” Schmidt said. “I’ve had them right on my face and in my hair, climbing around on me. I haven’t been bitten.”
Further research is still necessary to completely rule out any negative impacts Jorōs could pose on our environment, but in the meantime, experts stress going easy on broad pesticides.
“In trying to kill the spiders,” said Schmidt, “other beneficial insects feeding on pests in our yards will be impacted, and you’ll increase the likelihood of having a bunch of really difficult pests show up because you killed off some of the good guys out there.”
Read More: Over 100,000 Unlikely Spider Species in a Cave Built the Largest Web in the World
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article includes information from a study published in PLOS One: DNA metabarcoding to estimate diet overlap between the introduced Joro spider (Trichonephila clavata) and three native orb-weaving spiders
