“Giant” spiders no cause for alarm – CCN

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Joros spin (UGA/Jeremy Howell)
Joros spin (UGA/Jeremy Howell)

First it was armadillos and nutria rats, then hammerhead sharks and ‘murder hornets’ – and now flying spiders.

Invasive Joro spiders with four-inch legs and the habit of spinning webs to fly have made national headlines in recent days, leading to viral posts on social media and near-hysteria in some communities in the northeastern states. NC State University reports that the spiders have been in the United States for years and are slowly making themselves at home on the East Coast after being accidentally imported into Georgia.

Joros resemble common garden orb weavers – often called “Charlotte Spiders,” from the beloved children’s book and movie – but they are considerably larger. The average orb spider has legs five to ten centimeters long, while Joros can have legs ten centimeters or longer. Both spiders have black and yellow markings, smooth skin and spindly legs.

The spiders also migrate by spinning webs that allow them to ‘fly’ (technically float) for miles.

As if a flying spider isn’t enough for most arachnophobes, Joros are also poisonous. Joros also have extremely small mouths, making it difficult for them to bite a human even if they are inclined to do so. Their venom is not as poisonous as the average fire bite, and is generally not used as a weapon. Instead, bites are used to immobilize prey trapped in the spider’s intricate webs.

The good news is that their bites are harmless to humans, according to entomologists from NC State and the University of Georgia (UGA).

The East Asian Joro spider (Trichonephila clavate) apparently first emerged in Georgia around 2013. The species is native to Japan, Korea, Taiwan and China, and like fire breathers and other invasive insects, hitchhiked to America via shipping containers.

NC-StateBlack and yellow garden spider
Black and yellow cross spiders can be mistaken for Joros spiders. (NCSU)

Amitesh Anerao and Andy Davis from the University of Georgia recently published a study on Joro spiders.

Their UGA research found that Joro spiders actually freeze when they encounter humans, and will try to retreat. Study participants used turkey basters to blow puffs of air onto Joros, and after being frozen in place for ten seconds to an hour, the spiders fled.

“They are essentially closed and waiting for the disruption to clear,” Davis said in the study. “Our research shows that these spiders are actually more afraid of you than the other way around.”

UGA and NCSU both note that Joros is not particularly competitive with native spider species. They eat insects and on rare occasions the spiders kill and eat small birds that become entangled in a larger Joro web.

Joros also like to eat cockroaches and palmetto insects, which could explain why they adapt very well to urban environments where common orb weavers have smaller prey. Because they freeze when confronted with noise or activity, the paper says they can save energy, allowing them to persist in busier urban environments.
However, their webs can be large: Joro spider webs have been documented between power lines and over awnings at gas stations.

Both universities say the spiders are here to stay.

“One thing this article tells me is that the rapid spread of the Joros is due to their incredible reproductive potential,” Davis said. “They simply outshine everyone else. It is not because they crowd out native spiders or kick them out of their own web.”

Sightings of Joros have been reported to NCSU from western North Carolina since 2022, but entomologists say the spiders’ high birth rate and adaptability mean the spider will eventually spread statewide. Biologists ask that sightings of Joros spiders be reported to the Cooperative Extension or the NC State Plant Disease and Insect Clinic. They do ask that you be sure you are not reporting the common golden orb weaver or other species that look like Joros.

Unlike native orb weavers, Joros typically do not have the telltale crosshatch pattern in their webs that characterizes ‘writing’ spiders.

For more information, visit https://homegrown.extension.ncsu.edu/2022/06/joro-spider-just-the-facts/.