''Utivarachna arcuata'' is a species of spiders in the family

Trachelidae Trachelidae is a family of araneomorph spiders (more recently evolved spiders with inward-pointing chelicerae) first described by Eugène Simon in 1897 as a subfamily called "Tracheleae" ("Trachelinae" in modern terminology). The Trachelidae fam ...

found only in

Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

of China. It was described in 2014 by Li Zhao and Xian-Jin Peng. Adult males reach to long, while females can be to long. It closely resembles the

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

species ''

Utivarachna rama ''Utivarachna'' is a genus of Asian araneomorph spiders in the family Trachelidae first described by Kyukichi Kishida in 1940. It was largely ignored until Christa L. Deeleman-Reinhold revised the sac and ground spiders in 2001, transferring s ...

'', but there are several distinct differences. The back part of the

palpal bulb The two palpal bulbs – also known as palpal organs and genital bulbs – are the copulatory organs of a male spider. They are borne on the last segment of the pedipalps (the front "limbs" of a spider), giving the spider an appearance often desc ...

is semi-spherical, the tip of the embolus is only about a fifth as long as the basal part, the tibial apophysis is slightly tapered, the copulatory opening is on the back of the

epigyne The epigyne or epigynum is the external genital structure of female spiders. As the epigyne varies greatly in form in different species, even in closely related ones, it often provides the most distinctive characteristic for recognizing species. ...

, the back bursae are longer and thinner, and the connecting ducts are spaced farther apart. In Latin, the term "arcuata" means "curved". This name refers to the curved shape of the bottom part of embolus, the small, thin extension on the palpal bulb of the

pedipalp Pedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicerae ("jaws") a ...

References

Trachelidae Spiders described in 2014 Spiders of China {{Trachelidae-stub