It’s a deeply human experience to recoil from spiders. Imposing, syringe-thin legs, menacing fangs, the implied threat of a deadly or paralytic venom percolating within their cephalothoraxes, waiting to be unleashed. Egg sacs, cobwebs and exsanguinated husks — all that they leave behind.
Helpful as they may be for controlling household pests, arachnids are just plain frightening to most. But at least they don’t fly, right?
Right?
Recent research suggests that an invasive species of large, colourful spiders that take to the air as babies could spread to Canada.
Here’s what to know about joro spiders, the surprisingly timid, paratrooping predators that may creep and crawl north in the coming years, but for which doubts remain on when that might be, and just what impact they could actually bring.
Flight of the Arachnes
Known to scientists as trichonephila clavata, the joro, or “parachute” spider, is a species native to eastern Asia, but that has been observed cropping up in the southeastern United States for the past decade. Environmental research has found that the creatures could comfortably live much further north, though, with the potential to inhabit the Great Lakes, St. Lawrence and even Rocky Mountain regions — at least, in theory.
Capable of growing up to 10 centimetres or more in length, with intricate patterns of black, blue, magenta and lemonade-yellow on its carapace, the joro makes for an intimidating image, but it’s during infancy that they display their most headline-grabbing behaviour.
One of the species’ more fascinating characteristics is its tendency to “balloon,” an indirect form of flight accomplished by catching the wind on strands of spider’s silk. It’s common shortly after hatching among joros and their orbweaver cousins, a tactic used to escape the crowd of their many new siblings while they’re still small enough to be lightweight.
But while the sight of an eight-legged parasailor is certainly something to behold, researchers are focused on joros moving on a different scale: invasion.
“Where the wind blows, the spiders will be able to disperse,” said Cornell University ecologist Linda Rayor, in an interview with CTVNews.ca. “The thing is that they don’t have a whole lot of choice of where the wind is going.”
Near as researchers can tell, joros first appeared in the United States in the early 2010s, spotted in the northern Georgia after hitching a ride on some form of international cargo, prevailing theories suggest.
Since then, joros are confirmed to have spread into North and South Carolina, as well as Tennessee, with breeding populations suggested to exist even further afield and sightings reported in Alabama, Maryland, Oklahoma and West Virginia.
One study estimated their presence across a swath of land 120,000 square kilometres in size, and an online community monitoring site has logged thousands of “research-grade” observations of the species in North America since its emergence.
A study published by a multistate team of researchers in November found that, taking into account environmental data and analyzing their existing distribution, joros had the potential to spread, and spread north.
“much of eastern North America, along with pockets of the (w)est, are climatically suitable for T. clavata,” the study concludes. “All four models also predicted portions of Canada, including provinces north of the Great Lakes, such as Quebec and Ontario, as well as more fragmented portions of Alberta and British Columbia as potential habitat.”
In fact, the study found that southern Canada and the northeastern U.S. might be preferable climates for joros to those where they currently reside, with cooler temperatures further north “likely not [to] impede continued range expansion.”
A separate study out of East Tennessee State University this April estimates that more than 2.5 million square kilometres of North American land could be more than 50 per cent suitable for the joro; a vast area spanning the U.S. east and northeast, as well as southern Ontario, Quebec, the Maritimes and Newfoundland.
That said, the potential spread remains purely theoretical, and as far as the near future goes, Cornell’s Rayor argues that Canadians and her fellow New Yorkers alike shouldn’t hold their breath.
“It’s taken them 10 years to move into neighbouring states around northern Georgia,” she said. “It’s incredibly unlikely that they are going to be here, if they get here at all, for at least 10 years.”
Bad for spiders, benign for people?
If joros ever do parachute their way into Canada, Rayor says it’s not the end of the world.
“This is a wonderful opportunity for those of us further north to watch this stunningly beautiful spider in our yards,” read her remarks for a 2022 Cornell explainer on the joro.
At the time, Rayor noted a lack of concrete evidence that joros posed an ecological risk. Since then, some research has shown they may be outcompeting local spiders, tentatively evidenced by waning biodiversity in areas known to have fallen under the invasive species’ spread.
“Overall, very little is known about this species in its new North American range, especially its impacts within this novel ecosystem,” the multistate research team wrote in an article released early last year.
“We advise journalists and experts alike against exaggerating its potential environmental impact or uncritical acceptance of the spider as ecologically harmless.”
This custom Google map shows ‘research-grade’ observances of joros spiders in North America. While more than 3,000 such sightings have been recorded since 2017, none have occurred north of Maryland. (Google MyMaps, with data from the Global Biodiversity Information Facility, plotted by Charlie Buckley, CTV News)
Even so, Rayor maintained in a Thursday interview that as invasive species go, joros were far from the most destructive, pointing instead to the so-called “murder hornets” that threaten honeybee populations or emerald ash borers, wood-boring beetles that can defoliate whole species of trees.
Joros, she said, are better compared to cicadas — noticeable, but not very consequential.
“It’s bad news in terms of invasive species that are affecting native populations, but I think on a really large scale, this is not a big problem,” she said. “I personally would be absolutely bloody thrilled to have them in my backyard.”
And for the arachnophobes among us, she says there’s little to fear — joros pose no direct threat to humans, nor pets.
“With these big orbweavers, short of picking them up and putting your finger under their fangs, they’re not going to bite you,” she said.
She’s not alone in the assessment. A University of Georgia study published last spring found joros to be among the most timid spider varieties observed, displaying a “startle” response of total immobility for an hour or more when disturbed by a brief puff of air, rather than growing aggressive or even fleeing.
“Members of this genus are exceptionally shy,” the study said. “This extreme thanatosis response appears to be unprecedented.”
In the end, if a few bright yellow, palm-sized spiders set up shop in your yard, you’re likely going to be the one causing trouble for them.
“I know nobody wants to walk into a web, but spiders are awesome,” said Rayor.
