Ken Baker: Any reason to fear invasion of giant flying spiders?


Ken Baker
Tue, March 22, 2022, 

"Large, Parachuting Spiders Could Soon Invade the East Coast, Study Finds. –Smithsonian Magazine, March 8, 2022.

Nothing like a giant flying spiders story to brighten up your morning news feed. As if there weren’t enough trouble in the world. Really?

Well, yes and no.

I wonder if it’s possible to set aside our arachnophobia for a few paragraphs to take a relatively clear-eyed look at what’s currently understood about America’s newest invasive species, Trichonephila clavata, the Joro spider from Asia.

I admit that finding a spider scuttling across the carpet gives me the creeps. But I think it needs to be said that spiders are not evil and they are not out to get us. Obviously. And yet the outsized fear spiders trigger in so many of us makes you wonder.

Joro ascribed powers it does not possess

Yes, they can bite if threatened, and all spiders have some level of toxicity to their venom. But it’s one thing to recognize the potential threat posed by an animal and to deal with it — say by nervously avoiding, removing, or killing it — and something else again to sweat bullets while doing so because we’ve invested the creature with powers and intention it doesn’t possess.

The joro spider, a native of Asia, has become a common sight in neighborhoods in Athens and across Northeast Georgia.

Of the 20 or so cover stories I’ve read on the introduction and spread of Joro spiders in the Southeast, almost all refer to a single paper by Andrew Davis and Benjamin Frick published in the February 2022 issue of Physiological Entomology.

According to that report, the first observations of a new orb web-weaving spider began coming in from residents of northeastern Georgia in 2014. Specialists soon identified it as the Joro spider, which is native to Japan, Korea, Taiwan, and China. It is believed to have arrived as a stowaway on oceanic shipping containers (likely as eggs rather than adults).

Since then, the species has rapidly spread throughout the northern portions of the state and is now also found in South Carolina, North Carolina, and Tennessee. One specimen was reported in 2021 from Oklahoma by a woman who had recently traveled from Northeastern Georgia. The spider (which she euthanized) had apparently hitched a ride on her car, illustrating one of the principle ways the species is expected to colonize new areas.

Named for mythological Japanese spider

The species is named after Joro-gumo, a mythological spider of Japanese folklore that could morph into a beautiful woman (with a penchant for seducing and then devouring men). The females do get quite large, with a body length of about an inch (similar to that of our common garden spider), and long, spindly legs that would cover the better part of your palm, if you were to let her rest there for a spell.

And she is brilliantly colored. The back of Joro’s bright yellow abdomen is crossed by a series of blue-green stripes, there’s a red blotch toward the rear of the underside, and her black legs are each adorned with several yellow-orange bands. The quarter-inch long brownish male is seldom seen (except when courting a female on her web).

While I’ve read several descriptions stating the female’s fangs are too small to pierce human skin, others suggest its bite can be painful. All reports, however, observe that she is not aggressive, only biting in self-defense, and that her venom is not dangerous to humans.

But it will be the female’s web that is most likely to prove a nuisance. They can reach a diameter of 3three to six feet across, hanging from the vegetation of trees and bushes, telephone poles, gutters and porches. Intriguingly, in good sunlight, the silk of the web shines with a rich golden luster.

Most (but not all) experts feel there seems little to stop Joro’s spread throughout the Eastern coastal states and, some suggest, the rest of the nation wherever there’s adequate prey and structure to support its webs. Its range in Japan covers a similar span of climatic conditions to those seen in the Eastern U.S., and experiments reported in the Davis and Frick paper suggest that adults, which breed in the fall, should be able to handle autumn in the northern states.

Only baby spiders can balloon across the sky

That said, no publications have yet reported on how the eggs, which hatch out in the spring, might manage the subzero conditions of winter in the northern states.

And finally this: There will be no large spiders parachuting out of the sky. Only baby spiders can disperse by air. The process, more appropriately called ballooning, entails a spiderling spewing out a thin strand of silk into the air. On a good day (when the atmospheric conditions are just right) a passing breeze can carry the silk, with its tiny spiderling in tow, for many miles.

If you’ve ever had to claw a silken strand off your face while hiking a woodland trail, you’ve experienced evidence of the process, which is a common method of dispersal for many species of spiders.

Ken Baker is a retired professor of biology and environmental studies. If you have a natural history topic you would like Dr. Baker to consider for an upcoming column, please email your idea to fre-newsdesk@gannett.com.

This article originally appeared on Fremont News-Messenger: Ken Baker: How fearsome are giant flying Joro spiders?