The Joro spider, a large and strikingly colored species, is causing quite a stir as it expands its territory across the United States. Originating from East Asia, these spiders have established populations in the South and along the East Coast for years. Experts predict it’s only a matter of time before they become widespread throughout much of the continental U.S. This has led to a lot of questions, and perhaps a little alarm, about these newcomers – particularly, the question: Can Joro Spiders Fly?
While the idea of large spiders taking to the skies might sound like something from a horror movie, spider experts assure us that widespread panic is unwarranted. “My sense is people like the weird and fantastic and potentially dangerous,” notes David Nelsen, a biology professor at Southern Adventist University, who has been tracking the Joro spider’s expanding range. “This is one of those things that sort of checks all the boxes for public hysteria.” Instead of focusing on sensationalism, scientists emphasize that the real concern lies in the broader issue of invasive species and their potential harm to agriculture and ecosystems.
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Hannah Burrack, professor and chair of the entomology department at Michigan State University, echoes this sentiment. She describes the Joro spider as a “canary in the coal mine” species – highly visible and attracting attention, but ultimately less damaging than other, less noticeable invasive pests like certain fruit flies or tree borers. These less conspicuous invaders pose a more significant global threat to conservation, agriculture, and even human health.
What Exactly is a Joro Spider?
Joro spiders belong to the orb-weaver family, a group known for constructing impressive, wheel-shaped webs. Native to East Asia, they are easily identifiable by their vibrant yellow and black markings. When their legs are fully extended, these spiders can reach a considerable size, up to three inches (8 cm) in length.
Despite their potential size as adults, Joro spiders are currently quite small and inconspicuous, about the size of a grain of rice early in their life cycle. However, keen observers might spot their characteristic softball-sized webs on porches or the delicate golden silk threads that they leave across lawns. Adult Joro spiders are most commonly observed later in the year, particularly in August and September.
Joro Spider Expansion: Where Are They Headed?
Researchers are actively working to map the spread of Joro spiders. David Coyle, an assistant professor at Clemson University, collaborating with Nelsen on range studies, indicates that the primary Joro spider population is centered around Atlanta, Georgia, and is expanding into the Carolinas and southeastern Tennessee. A separate, smaller population has also been identified in Baltimore, Maryland, in recent years.
Predicting the future range of these spiders, particularly their arrival in the Northeast, is still uncertain. Coyle suggests, “Maybe this year, maybe a decade, we really don’t know. They’re probably not going to get that far in a single year. It’s going to take a bunch of incremental steps.” The expansion is expected to be gradual, rather than a sudden surge.
Addressing the Key Question: Can Joro Spiders Actually Fly?
The answer to the question “can Joro spiders fly?” is nuanced. Adult Joro spiders, with their relatively large size, are not capable of true flight. You won’t see adult Joro spiders soaring through the air. However, young Joro spiders possess a remarkable ability called “ballooning” that allows them to travel long distances on air currents.
Ballooning is a dispersal method used by many spider species. Young spiderlings, being very light, spin silk threads that catch the wind. These silk threads act like tiny parachutes, lifting the spiderlings into the air and carrying them, sometimes for miles. Furthermore, research has shown that spiders can also utilize Earth’s electric field to aid in ballooning, making their aerial journeys even more efficient. This explains how Joro spiders, originating from Asia, are able to colonize new territories far from their original habitats and effectively “fly” across regions as spiderlings.
What Do Joro Spiders Eat and What’s Their Ecological Role?
Joro spiders are not picky eaters; they are opportunistic predators that will consume any insects that become trapped in their webs. This primarily includes various insect species. While this might suggest competition with native spider populations for food resources, there could also be a beneficial side. Andy Davis, a research scientist at the University of Georgia, has observed that Joro spiders’ daily catches can also serve as a food source for native bird species, indicating a potential integration into the local food web.
Regarding the hopeful idea that Joro spiders might control populations of the invasive spotted lanternfly, which is causing significant damage to trees on the East Coast, experts are less optimistic. While Joro spiders may occasionally prey on spotted lanternflies, Coyle states there is “zero chance” they will significantly impact lanternfly populations.
Are Joro Spiders a Threat to Humans?
Despite their intimidating size and vibrant colors, Joro spiders are not considered dangerous to humans. Like all spiders, they possess venom, but Joro spider venom is not potent enough to be medically significant to humans. According to Nelsen, a Joro spider bite might, at worst, cause minor itching or a localized allergic reaction. However, these spiders are generally shy and tend to avoid human interaction. Bites are infrequent and typically occur only when a spider feels directly threatened.
The real danger, as scientists emphasize, lies in the broader spectrum of invasive species, such as the emerald ash borer or the spotted wing drosophila fruit fly. These less conspicuous invaders pose a greater threat to natural resources and ecosystems than Joro spiders.
Andy Davis reflects on the bigger picture: “I try to stay scientifically objective about it. And that’s a way to protect myself from maybe the sadness of it. But there’s so much ecological damage being done all over the world for, for so many reasons, mostly because of humans,” Davis says. “This to me is just one more example of mankind’s influence on the environment.” The Joro spider serves as a visible reminder of the ongoing impact of global interconnectedness and environmental change, prompting us to consider the broader implications of invasive species beyond just the fear of a large, colorful spider in our backyard.
