Despite 250 years of taxonomic classification and over 1.2 million species already catalogued, known species diversity is only a small part of true species diversity on Earth, and thus, the known species are only the tip of iceberg. Here, we investigated the genus Pholcus Walckenaer, 1805 of the family Pholcidae C. L. Koch, 1850 in the Changbai Mountains, Northeast China, which provides an excellent case of high species diversity. Previously, only 14 endemic Pholcus spiders, all belonging to the P. phungiformes species group, and two introduced species P. manueli Gertsch, 1937 and P. zichyi Kulczyński, 1901 from the P. crypticolens species group, have been recorded from this area. Our study confirmed 11 new species of the P. phungiformes species group based on morphology and three methods of molecular species delimitation: P. gaizhou Yao & Li, sp. nov., P. guanshui Yao & Li, sp. nov., P. jiguanshan Yao & Li, sp. nov., P. longxigu Yao & Li, sp. nov., P. luoquanbei Yao & Li, sp. nov., P. shenshi Yao & Li, sp. nov., P. tianmenshan Yao & Li, sp. nov., P. wangjiang Yao & Li, sp. nov., P. xingqi Yao & Li, sp. nov., P. yaoshan Yao & Li, sp. nov., and P. yuhuangshan Yao & Li, sp. nov. This study brings the fauna of the P. phungiformes species group from the Changbai Mountains to 25 species, approximately two times more than previously known, which could indicate that species diversity in the area is underestimated for all arthropod fauna.

Spiders of the genus Pholcus were collected for the first time during an expedition to the Lüliang Mountains in Shanxi Province, North China. Phylogenetic analyses of DNA sequence data from COI, H3, wnt, and 28S genes allowed us to group them into nine well-supported clades. We used morphology and four methods of molecular species delimitation, namely Automatic Barcode Gap Discovery (ABGD), the Generalized Mixed Yule Coalescent (GMYC), Bayesian Poisson Tree Processes (bPTP), and Bayesian Phylogenetics and Phylogeography (BPP), to investigate species boundaries. These integrative taxonomic analyses identified the nine clades as nine distinct species, comprising Pholcus luya Peng & Zhang, 2013 and eight other species new to science: Pholcus jiaocheng sp. nov., Pholcus linfen sp. nov., Pholcus lishi sp. nov., Pholcus luliang sp. nov., Pholcus wenshui sp. nov., Pholcus xiangfen sp. nov., Pholcus xuanzhong sp. nov., and Pholcus zhongyang sp. nov. The species occur in geographic proximity and show many morphological similarities. All of them belong to the P. phungiformes species group. The records from the Lüliang Mountains represent the westernmost distribution limit of this species group.

We report 18 spider species of the genus Pholcus Walckenaer, 1805 from a survey in the Qinling Mountains of central China. They belong to four species groups and include seven species new to science: Pholcus jiaozuo Yang & Yao, sp. nov. (♂♀) in the taishan species group; P. luonan Yang & Yao, sp. nov. (♂♀), P. luoyang Yang & Yao, sp. nov. (♂♀), P. lushan Yang & Yao, sp. nov. (♂♀), P. shangluo Yang & Yao, sp. nov. (♂♀), P. weinan Yang & Yao, sp. nov. (♂♀) and P. yuncheng Yang & Yao, sp. nov. (♂♀) in the yichengicus species group. Detailed diagnoses, descriptions, photomicroscopy images and DNA barcodes of all new species are provided. Our study will make a significant contribution to understanding species diversity and zoogeography of the region.

Four morphologically similar species of the Pholcus yichengicus species group, occurring in geographic proximity of China’s Qinling Mountains, were recognised, based on morphology and four methods of molecular species delimitation. They comprise two new species, namely Pholcus ankangsp. nov. and P. baojisp. nov. and two previously described species: P. ovatus Yao & Li, 2012 and P. taibaiensis Wang & Zhu, 1992. Their DNA barcodes were obtained to estimate p-distances and K2P distances. In addition, an identification key for the four closely-related species is presented.

Species of the Pholcus phungiformes group exhibit high diversity in Liaoning Province of northeastern China. This paper summarizes the current knowledge on this species-group from this area. A checklist of 22 species recorded from this province is given, accompanied with a distribution map of the species. Pholcus xiuyan Zhao, Zheng & Yao, sp. nov. (♂♀) is described as new to science, and P. yuhuangshan Yao & Li, 2021 is reported from Liaoning for the first time.