Jorō Spiders Increase Population in the US But Mean No Harm to People

The residents in the US East Coast may have noticed more Joro spiders over the past years, and yet, their population continues to increase in the region.

In a report of Scitech Daily, Joro spiders could have been in millions now and these invasive species have rapidly spread across the Southeast.

Scientifically known as the Trichonephila clavate, the black and bright yellow Joros are huge and can fit the size of the palm, wherein the body size of an adult female is at 17-25mm while the male is at 7-10 mm. However, there is nothing much to worry about these arachnids.

They are gentle, not aggressive

In a science journal published by Andrew Davis and Amitesh Anerao of University of Georgia, they described Joros spiders as the "shyest" ever documented.

During an 'air puff' response conducted that tests the reaction to perceived threats, Joro spiders remained immobile for over an hour, compared to other spider species that will mostly remain immobile for only under a minute after a stimulus.

The same was observed with Joros' cousin, the golden silk spider which both came from the same genus.

"After a mild stressor, both Trichonephila species displayed an exceptionally prolonged thanatosis reaction (over 1 hour), compared to other spider species, which had reactions lasting for only minutes," the researchers noted.

They concluded through their study that these kinds of spiders can tolerate continuous disturbances in urban-living.

In a separate study, Davis said that people should try to live with Joro spiders.

While they are considered venomous, these spiders are not a threat to humans or even pets. Even if they are large in size, Joro spiders' defensive bites are not fatal and most likely wouldn't break the skin because their fangs are small according to Earthsky.

Joros as pest controls

University of Georgia entomologist Nancy Hinkle told USA Today that Joro spiders can be a valuable pest control, as they feed on insects like mosquitoes, flies, and stink bugs.

With this, there are more natural methods to suppress pests instead of using chemicals.

"I'm trying to convince people that having zillions of large spiders and their webs around is a good thing," Hinkle said.

Joro spiders originated in East Asia and native to Japan, Korea, Taiwan, and China. The spider shares its name with a folkloric "spider demon" in Japanese culture.

These spiders were first spotted in Georgia, wherein it is believed to be brought to the United States in 2013 through shipping containers from Asia. Since then, they have become an invasive species to the Southeastern part of the US and they may start to migrate and colonize other parts of the east coast.

With the help of their webs, they can fly through the air through a technique that scientists called as "ballooning". Joro spiders are also observed to have great ability to adapt in cold temperatures, which also makes it easy for them to spread in many areas.