A new cave-dwelling spider of the genus Speleoticus (Araneae, Nesticidae) from Sichuan, China

Abstract Background Speleoticus Ballarin & Li, 2016 is a relatively small spider genus of the family Nesticidae, currently including five cave-dwelling species, distributed exclusively in East Asia, four of which are known from China. New information A new troglobitic spider of the genus Speleoticus from the limestone Cave Hanwang Dong, north-eastern Sichuan, China, is described under the name of S.hei Yu & Lin, sp. n. Detailed descriptions, photographs and a distribution map of the new species are provided.


Introduction
Speleoticus Ballarin & Li, 2016 is a small nesticid genus that is distributed exclusively in East Asia, with only five species described so far: S. uenoi (Yaginuma, 1972) endemic to Japan, S. globosus (Liu & Li, 2013), S. libo (Chen & Zhu, 2005), S. navicellatus (Liu & Li, 2013) and S. yinchangminae Li, 2016 from China (Liu and Li 2013, Lin et al. 2016, World Spider Catalog 2023. Speleoticus is a troglobitic spider genus and all known species are restricted to caves and exhibit a high level of adaptation to the troglobitic life: some species possess a distinct set of somatic characters, such as depigmentation, eyes reduction and elongation of legs (Lin et al. 2016).
The monophyly of Speleoticus is well defined by its genitalic characteristics (see Lin et al. (2016) for diagnoses of the genus). All Speleoticus species were known from both sexes and have been described in detail, alongside high quality illustrations, to allow easy species recognition (Yaginuma 1972, Chen and Zhu 2005, Yin et al. 2012, Liu and Li 2013, Lin et al. 2016. Recently, various expeditions to the limestone cave Hanwang Dong, north-eastern Sichuan, China (Guangyuan City: Chaotian District) ( Fig. 1A-C) were carried out by colleagues of the Sichuan Cave Exploration Team (SCET, Chengdu, the cave biology group led by Mr. Li He) (Fig. 1D, E). During these surveys, we found some specimens of cave-dwelling spiders seemingly belonging to the family Nesticidae (Fig. 2). All specimens possess diagnostic characters which define them as belonging to the genus Speleoticus, but can be easily distinguished from the other Speleoticus species. The goal of this paper is to provide a detailed description and diagnosis of the new species.

Materials and methods
Specimens in this study were hand collected. The type specimens are deposited in the Museum of Guizhou Normal University, Guiyang, Guizhou, China. Specimens were preserved in 75% alcohol and examined using an Olympus SZX7 stereomicroscope. Left male palps were examined and illustrated after dissection. Epigynes were removed and cleared in a warm 10% potassium hydroxide (KOH) solution. The vulva was photographed after being embedded in Arabic gum. Images were captured with a Canon EOS 70D digital camera (20.2 megapixels) mounted on an Olympus CX41 compound microscope and assembled using Helicon Focus 6.80 image stacking software. All measurements were obtained using an Olympus SZX7 stereomicroscope and are given in millimetres. Eye diameters were measured at the widest part. The total body length does not include the chelicerae or spinnerets. Leg lengths are given as total length (coxa, trochanter, femur, patella+tibia, metatarsus, tarsus). The terminology used in the text and figure legends follows Liu and Li (2013) and Lin et al. (2016). The distribution map was generated with ArcGIS v. 10.5 (Environmental Systems Research Institute, Inc.).

Etymology
This species is a patronymic named after Mr. Li He (Chengdu City, China), collector of the types, who has greatly helped us in our research.

Biology
The types of S. hei Yu & Lin, sp. n. were collected under stones in the moist area about 50-500 m from the entrance in Hanwang Dong Cave.