By 
University of Georgia College of Agricultural and Environmental Sciences
Giant, invasive Joro spiders have expanded across several U.S. states during the last decade. Now, scientists have invented these palm-size critters are potentially much more tolerant to living in cities than other species and appear to develop alongside major roads, which could help give them a foothold (or eight) in major cities along the Eastern Seaboard.
Joro spiders (Trichonephila clavata) are a species of orb-weaving spiders — a group known for making highly symmetrical, circular webs. Joros are easily observable thanks to the differentiative yellow bands that adorn their otherwise black legs. They also create unique webs that can be more than 6 feet (1.8 meters) across and look golden when they reflect sunlight.
Female Jorōs, which can grow to around 3 inches (7.6 centimeters) across — around double the size of males — also have blue stripes and red patches on their predominantly yellow abdomens.
After mating in early autumn, female Jorōs lay large, web-bound clusters of up to 400 eggs before dying off at the start of winter, along with the males. When the eggs hatch in spring, the little baby spiders make parachute-like webs that enable them to fly up to 100 miles (160 kilometers) away from where they were born.
Joro spiders are endemic to Asia, and until recently they were only found in Japan, Korea, Taiwan and China. However, in 2014, researchers detected several Jorōs in the U.S. near Atlanta, Georgia. Experts believe these invasive individuals were accidentally brought to the U.S. inside a shipping container, according to a 2015 study.
In the years since, Jorō spiders have rapidly risen and spread in the U.S. 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 noted in Alabama, Maryland, Oklahoma and West Virginia, and experts believe they could spread across the entire U.S. East Coast in the future.
Since their arrival, researchers have reported that Jorō webs are mostly located in close proximity to major highways. This is shocking because the vibrations caused by busy roads normally interfere with spiders‘ ability to hunt: When smaller critters get stuck in spider webs, they fight to get out from it, which alerts the spiders to their presence, but busy roads can drown out these vibrations. Spiders are also very sensitive to vibrations in general.
In a new study published Feb. 13 in the journal Arthropoda, researchers inquired how vibrations effected Jorō spiders. In the laboratory, the study team used tuning forks to simulate the vibrations given off by highways to see how it effected 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 similar healthy body weight to the other spiders, indicating that the vibrations were not effecting 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 not sure what long-term impacts Joro spiders will have on the ecosystems they conquer. Last year, scientists showed that the spiders are unusually shy and non-aggressive toward other spiders. However, without a natural predator looking them out, their numbers will continue to grow, which could help them outcompete other species for resources.
Beside their ecological impacts, the new discovery suggest these arachnid invaders aren’t going anywhere anytime soon.
“I m not aware 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 thought a spider to be,” she added.
