A newly recorded genus with description of a new cave-dwelling species of Flagelliphantes (Araneae, Linyphiidae) from northeastern China

Abstract Background The genus Flagelliphantes Saaristo & Tanasevitch, 1996 was proposed by Saaristo & Tanasevitch, 1996 to accommodate three ex-Lepthyphantes species distributed in northern Eurasia. Male Flagelliphantes are easlily recognised by having a hood-shaped thumb on the embolus. The females have a long, S-shaped scape and the posterior median plate of the epigyne is grossly enlarged (“hypertrophied”). New information While examining Linyphiidae Blackwall, 1859 specimens from Yunxia Cave in China’s Jilin Province, we discovered a new cave-dwelling species of the genus Flagelliphantes, F.yunxia sp. n. In this paper, we provide detailed description and photos of its diagnostic somatic and genitalic features. It is the first record of the genus from China.

This paper adds another new species of this diverse family in China and constitutes the first record of genus Flagelliphantes of the country. It is a cave-dwelling spider, found in Yunxia Cave, located at Tonghua Municipality of Jilin Province in northeastern China, bordering the northern parts of the Democratic People's Republic of Korea.

Materials and methods
Specimens were examined and measured with a Leica M205 C stereomicroscope. Left male palp was photographed. Epigyne was photographed before dissection. Vulva was treated in a 10% warm solution of potassium hydroxide (KOH) to dissolve soft tissues before illustration. Images were captured with a Canon EOS 750D wide zoom digital camera (24.2 megapixels) mounted on the stereomicroscope mentioned above and assembled using Helicon Focus 3.10.3 image stacking software (Khmelik et al. 2005). All measurements are given in millimetres (mm). Leg measurements are shown as: total length (coxa, trochanter, femur, patella, tibia, metatarsus, tarsus). Leg segments were measured on their dorsal side. Metatarsal trichobothrium (Tm) is given as the ratio of the distance between the proximal margin of the metatarsus and the root of trichobothrium divided by the total length of the metatarsus (Denis 1949, Locket andMillidge 1953) and Tm value for the first and the fourth leg is given as TmI, TmIV, respectively. The specimens studied are preserved in 75% ethanol and deposited in the College of Life Science, Shenyang Normal University (SYNU) in Liaoning, P.R. China. Terminology and taxonomic descriptions follow Saaristo and Tanasevitch (1996).

Abbreviations
Somatic morphology: ALE = anterior lateral eye; AME = anterior median eye; AME-ALE = the distance between AME and ALE; AME-AME = the distance between AMEs; PLE = posterior lateral eye; PME = posterior median eye; PME-PLE = the distance between PME and PLE; PME-PME = the distance between PMEs.

Etymology
The specific name refers to the type locality; noun in apposition.

Biology
The species was found in the aphotic zone inside cave.