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Trichonephila clavata
	Female
Conservation status
	; Least Concern (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Arachnida
Order:	Araneae
Infraorder:	Araneomorphae
Family:	Nephilidae
Genus:	Trichonephila
Species:	T. clavata
Binomial name
	Trichonephila clavata; (L. Koch, 1878)
Synonyms
	Nephila clavata L. Koch, 1878; Nephila limbata Thorell, 1898; Nephila obnubila Simon, 1906; Nephila clavatoides Schenkel, 1953; Nephila clavata cavalierei Schenkel, 1963; Argiope maja Bösenberg & Strand, 1906;

Trichonephila clavata, also known as the Joro-spider (ジョロウグモ, Jorō-gumo), 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 rarely bites humans, and its venom is not deadly.

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 ten other species.^[3]

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 millimetres (0.67–0.98 in) while the male's is 7–10 millimetres (0.28–0.39 in).

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 1,500 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.^[4]

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.^[5] She seeks men to seduce, whom she then binds in her silk and devours.

This spider was about 5 cm long. The large one is the female and the smaller one in the background is the male - filmed in Tokyo, Japan on 29 September 2013

Introduced species in North America

The Joro spider is an introduced species in northeast Georgia and northwest/upstate South Carolina, in the United States. They were first spotted in Hoschton, Georgia, in 2013. Since then, they have been seen in numerous locations in northeast Georgia, including the Athens area and also in Greenville, South Carolina. It is believed that the species will become naturalized^{[by whom?]}. While the Joro spider was first observed in the warm climates of the Gulf and lower East Coast of the US, it is now expected to colonize much of the middle East Coast due to its relative imperviousness to modest cold.^[6]^[7]

Scientists confirmed the first known occurrence of T. clavata in North America in 2014,^[8] and as of October 2022, the spider's range spans at least 120,000 km² (46,000 sq mi), occurring across the US states of Georgia, South Carolina, North Carolina, and Tennessee, with additional reports in Alabama, Maryland, Oklahoma, West Virginia, and Pennsylvania. Its pattern of spread suggests it is primarily driven by natural dispersal mechanisms, such as ballooning, though human-mediated transport cannot be discounted.^[9]^[8]^[10]^[11]^[12]

The Joro spider has been spotted in many eastern US states, including Alabama, Kentucky, Maryland, Massachusetts, Mississippi, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Virginia, Florida, and West Virginia, and it appeared in the southern portions of New York and neighboring states sometime in the summer of 2024.^[13]^[14] The spiders "seem to be OK with living in a city", according to University of Georgia researcher Andy Davis, who added that he has seen them on streetlamps and telephone poles.^[13] In September 2024, one was photographed in Beacon Hill, Boston, Massachusetts.^[15]

As of 2022, because of the relative lack of information about the Joro spider's ecology, the impact it has on its new ecosystem is unknown. It has been observed catching the brown marmorated stink bug (Halymorpha halys), an invasive species that native spiders have not been known to eat, and there is hope that the impact of the species will be positive due to its harmless nature and consumption of primarily invasive or nuisance insects.^[7]^[16]