The U.S. Has Giant Invasive Spiders. Who Cares?
The joro spider poses no threat to humans and a lack of funding is delaying our understanding of their effect on the environment
Photo courtesy of David Coyle
Over the past few weeks, the headlines have been terrifying: large, yellow, poisonous airborne spiders will soon be scurrying into homes across a large portion of the northeastern United States.
The joro spider (or trichonephila clavata) is native to China, Japan, Korea and Taiwan and it is indeed an arachnophobe’s worst nightmare. The females of the species are bright yellow with intimidating black markings and have bodies that can grow to almost an inch long, with legs four times that length.
The bad news is that this spider has indeed invaded the United States - the first sighting in the country was a decade ago in Georgia, and it has since been spotted in several other states. But panicky news headlines have done a major disservice to science in general and this arachnid in particular. The truth is, the little buggers pose no threat to humans and what effect they may have on their new habitats remains unclear.
“We're only seeing this big pulse of work now, I think because their populations did explode in the last few years,” David Coyle, an assistant professor at Clemson University, told The Flatline. “And, you know, they're all over the place. They're big, they're spiders, they checked a lot of people's uncomfortable boxes.”
While even Wikipedia claims the joros are coming to New York and New Jersey as soon as this summer, confirmation of the claim is spotty at best. A CBS News article from early June cited only a New Jersey exterminator’s website, with the operators blaring that “giant venomous flying spiders” are coming to the state. While it’s possible the joro could soon be found in the northwest states, there’s no evidence they’ve spread that far as of yet. A website dedicated to tracking joro spottings shows the spiders have spread as far north as Maryland, but for now, the spiders remain concentrated in Georgia, Tennessee and the Carolinas.
“It was a blog written by Joe Blow, who doesn't really know what he's talking about,” said Andy Davis, an assistant research scientist at the University of Georgia who co-authored several studies on the joro. “He said something like the joro spider is coming to New Jersey any day now and that was it, and then that led to a local story in a local paper about that blog. They interviewed that guy. I saw one of the interviews. He's just a chucklehead.”
The misleading articles have frustrated researchers, who worry they could lead to misplaced fears of a misunderstood creature. Joros are venomous, but that venom only poses a threat to their prey. Spider venom in general is usually fairly harmless to humans, said Catherine Scott, an arachnologist and self-described spider advocate currently working on a postdoc at McGill University. There are notable exceptions such as the black widow, which has evolved to prey on small vertebrates, but the joro’s diet consists of insects.
“With the exception of black widows and recluse spiders, any other spider that you encounter in North America is not medically significant and, in general, bites are extremely rare because spiders don't feed on human blood, so they have no reason to bite us, unless they are threatened,” said Scott. “Bites happen when a spider has made its home in a jacket or boots that you've left outside, and then you put them on and crush the spider against your skin and as a sort of last resort defensive thing, the spider will bite. But their venom isn't for affecting humans.”
While it’s clear that joros pose no mortal threat to humans, what their arrival means for the environment remains unclear. Both Davis and Coyle have published a few studies that have begun to make that picture a bit clearer: Coyle found for example, that joros may be displacing many native species as they spread.
“We don't know what that means, long term, in terms of if you replace a diverse assemblage of stuff with one thing, I can't think of any instances where that's great long term,” he said. “There's always something that goes awry at some point. It's just a matter of when and what.”
Thanks to Davis, we now know that the spiders have little taste for monarch butterflies (though how they know not to eat the beloved but foul-tasting insects is still a mystery). We also know that it’s entirely possible the spiders could actually produce buffets for northern cardinals, at least one of which was spotted picking out bugs from a joro’s web. Davis said he’s even spotted some smaller, native spiders stealing food from the joros.
“Everybody's sort of looking to find negative effects,” he said. “And when you're looking to find negative effects, you're going to find them. No one is looking to find positive effects.”
The truth of the matter is that since joros are not particularly harmful to humans and pose no threat to agriculture, funding for studies on their impact in North America is hard to come by. Contrast that to another invasive insect, the spotted lanternfly, whose spread to the east coast not only resulted in local governments begging residents to stomp on them, but also has led to a flurry of studies due to their harmful effects on several tree species (though at least one recent study found that threat to be overstated).
The lack of funding isn’t puzzling to Coyle, although it is frustrating.
“Anything with an ecological impact is always kind of last to the funding table, for lack of a better word, because the money goes towards human health, food security, those things kind of get prioritized over potential ecological impacts,” he said.
On a certain level, it’s understandable why some people might be freaked out by the joro’s spread: it’s a big bug from far away. But with so little known about what effect it will have on North American ecology and with the spiders posing no direct threat to humans, Coyle has been urging for sanity, authoring a recent journal article calling for more research and less hysteria.
“I think the whole flying, giant, venomous spiders is the worst possible word choice I could ever envision, yet, that's what gets out there, and all of a sudden it's the apocalypse,” he said. “So, yeah, I mean, they're spiders, there's a lot of arachnophobic folks out there. I get that they're colorful, they're big, they're non-native and their populations are increasing and spreading, like every other invasive species does. So that's four for four for a lot of people in the holy crap meter, and where we are.”
Despite the hysteria, Davis has chosen to look at the bright side of all the media attention.
“I almost see this as a positive, because everybody's out in their backyards looking at their spider fauna in their backyards. You know, they may be scared, maybe they're hearing bad things, but at least all of this attention is giving people more impetus to go in their backyards and just spend some time looking around,” he said. “I think that's sort of a good thing. Really, if you think about it, you can spend some time looking at a joro spider web and get to know them. They're going to be in that web for many months, that same place, that same spider, in the same tree, you can get to know their spider. You can teach your kids what these spiders do.”