Joro spiders can spread in US cities

Giant and invasive Jorō spiders have spread to several states in the US over the past decade. Scientists have now discovered that these palm-sized creatures are potentially much more tolerant to living in cities and appear to thrive alongside major roads, which could help them establish themselves in major cities along the Eastern Seaboard.

Jorō spiders belong to the orb-weaving spiders’ species, known for creating highly symmetrical, circular webs. The Jorōs are easily recognizable thanks to the distinctive yellow bands on their otherwise black legs. They also build unique webs that can be more than 6 feet across and appear golden when they reflect sunlight.

The females of the species can grow to around 3 inches across (7.6 centimeters), which is about double the size of males. They also have blue stripes and red patches on their predominantly yellow abdomens. After mating in early autumn, female Jorōs lay large clusters of up to 400 eggs, web-bound before dying off at the start of winter, along with the males. When the eggs hatch in spring, the baby spiders create parachute-like webs that enable them to fly up to 100 miles (160 kilometers) away from where they were born.

Jorō spiders are endemic to Asia and, until recently, were only found in Japan, Korea, Taiwan, and China. However, in 2014, researchers spotted several Jorōs in the US near Atlanta, Georgia. Experts believe that these invasive individuals were accidentally brought to the US inside a shipping container, according to a 2015 study.

Since their arrival, Jorō spiders have quickly multiplied and spread in the US, thanks to their ability to widely disperse after birth. They are now found across Georgia, as well as in South Carolina, North Carolina, and Tennessee. Additional sightings have also been reported in Alabama, Maryland, Oklahoma, and West Virginia, and experts believe they could spread across the entire US East Coast in the future.

Researchers have noticed that Jorō webs are often located in close proximity to major highways. This is surprising because the vibrations caused by busy roads normally interfere with spiders’ ability to hunt. Spiders are very sensitive to vibrations in general, and when smaller critters get trapped in spider webs, they struggle to get free, which alerts the spiders to their presence. However, busy roads can drown out these vibrations.

In a new study published on Feb. 13 in the journal Arthropoda, researchers investigated how vibrations impacted Jorō spiders. In the laboratory, the study team used tuning forks to simulate the vibrations given off by highways to see how it impacted the arachnids’ ability to hunt simulated prey placed in their webs.

Across 350 trials, vibrated Jorōs attacked simulated prey 59% of the time, while non-vibrated Jorōs pounced on the dummy prey 65% of the time. The trials also showed that the “roadside” spiders were able to maintain a healthy body weight similar to the other spiders, indicating that the vibrations were not impacting them in the long term.

“The spiders seem to be able to make a living there,” lead study author Andy Davis, an ecologist at the University of Georgia, said in a statement. They are surprisingly “urban tolerant,” he added.

It is still uncertain what consequences the invasion of Jorō spiders will have on the ecosystems they inhabit. Recently, researchers discovered that these spiders tend to be very timid and non-violent towards other spider species. However, since they don’t have any natural predators, their population is likely to increase, which could lead to them outcompeting other species for resources.

Regardless of their ecological impact, the latest findings indicate that these arachnid invaders are here to stay.

“I don’t know how happy people are going to be about it, but I think the spiders are here to stay,” study co-author Alexa Schultz, a third-year ecology student at the University of Georgia, said in the statement. And they could end up in places “where you wouldn’t imagine a spider to be,” she added.

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