Trichonephila clavata

Trichonephila clavata, also known as the Joro-spider (ジョロウグモ), is a spider in the Trichonephila genus. Native to East Asia, it is found throughout China, Japan (except Hokkaidō), Korea, and Taiwan, and has been spreading across North America since the 2010s. It is venomous, but it rarely bites humans and its venom is not deadly.

Scientists confirmed the first known occurrence of T. clavata in North America in 2014, and as of October 2022, T. clavata's range spans at least 120000 km2, occurring across the US states of Georgia, South Carolina, North Carolina, and Tennessee, with additional reports in Alabama, Maryland, Oklahoma, and West Virginia. Its pattern of spread suggests it is primarily driven by natural dispersal mechanisms, such as ballooning, though human-mediated transport cannot be discounted.

In 2019, this species was moved from the genus Nephila to Trichonephila. Another species from this genus, Trichonephila plumipes, is commonly found in Australia. It also was moved from Nephila to Trichonephila, along with 10 other species.

The Joro spider is expected to be in the southern portions of New York state and surrounding US states sometime in the summer of 2024, according to a June 5 CBS news article. The Joro spider has been spotted in the US states of Florida, Alabama, Mississippi, North and South Carolina, Tennessee, Kentucky, Virginia, West Virginia, Maryland and Ohio, according to CBS. The Joro spiders "seem to be OK with living in a city," said University of Georgia researcher Andy Davis, adding that he has seen the Joro spiders on street lamps and telephone poles.

Characteristics
Trichonephila clavata pass winter as eggs and scatter as tiny juveniles in the spring. Like most spiders, females are much larger than males. The adult female's body size is 17–25 mm while the male's is 7–10 mm.

The web of females may reach several meters in length. In sunlight, the yellow threads appear to be a rich gold color. The structure of the web seen in cross-section is unusual for an orb web; it has three layers: the central orb, plus two irregular layers in front and behind the orb.

Both males and females have large abdomen and long legs. The adult female individual has stripes of yellow and dark blue, with red toward the rear of the abdomen. In autumn, smaller males may be seen in the webs of the females for copulating. After mating, the female spins an egg sack on a tree, laying 400 to 1500 eggs in one sack. Her lifecycle ends by late autumn or early winter with the death of the spider. The next generation emerges in spring.

Risks to people
This spider's bite does not pose significant risks to humans. Their small fangs and reluctant biting behavior make it unlikely for a bite to occur. When bites do take place, the venom is weak. The temporary pain and redness has been compared to that of a bee sting.

In folklore
The common name of the spider comes from the jorōgumo, a legendary spider in Japanese folklore that can transform into a beautiful woman who can breathe fire and control other spiders. She seeks men to seduce, whom she then binds in her silk and devours.



Introduced species in North America
The spider is an introduced species in northeast Georgia and northwest/upstate South Carolina in North America. They were first spotted in Hoschton, Georgia, in 2013. Since then, they have been spotted in numerous locations in northeast Georgia, including the Athens, Georgia, area, and also in Greenville, South Carolina. It is believed that the species will become naturalized. While the Joro spider was first observed in the warm climates of the Gulf and lower East Coast, they are now expected to colonize much of the middle Eastern Seaboard of the United States due to their relative imperviousness to modest cold.

As of 2022, because of the relative lack of information about its ecology, their impact on their new ecosystem is unknown. They have been observed catching the brown marmorated stink bug (Halymorpha halys), an invasive species that native spiders have not been known to eat, and it has also been hoped that they may consume mosquitoes and flies, although flies, mosquitoes, and many other flying insects are consumed by native species of all sorts. Some hope that the impact of the species will be positive due to their harmless nature and consumption of primarily invasive or nuisance insects.