The present study describes Philodromus rufus Walckenaer, 1826 with detailed descriptions, taxonomic photographs, distribution map, and proposition of a new synonym. Due to morphological similarity between P. pseudoexilis Paik, 1979 and P. rufus, taxonomic identity of P. pseudoexilis has been doubtful to date. A detailed bibliographic study of types of P. pseudoexilis between P. rufus and examination of specimens from the type locality of P. pseudoexilis with specimens of P. rufus collected across the country showed that P. rufus has all diagnostic characters found in types of P. pseudoexilis. Therefore, P. pseudoexilis Paik, 1979 should be regarded as a new synonym of Philodromus rufus Walckenaer, 1826.

The present study describes Philodromus paiki sp. nov., which was previously misidentified as P. fuscomarginatus (De Geer, 1778), P. poecilus (Thorell, 1872), and P. spinitarsis Simon, 1895 in Korea, as a new species with diagnosis, detailed descriptions, and taxonomic photographs. Additionally, P. spinitarsis is also described to correct previous misidentifications of Korean records of the species.

A male Spheropistha melanosoma Yaginuma, 1957 from Korea in the family Theridiidae Sundevall, 1833 is described with measurements and morphological photos of the diagnostic characteristics. This species was collected with a sweep net around arable lands in a mountainous mixed forest during the investigation of spider fauna on Ulleungdo Island in 2019.

Two species of the genus Oxytate L. Koch, 1878 have been recorded in Korea to date. The spider fauna was surveyed in the mountainous terrain of Mt. Hallasan National Park in 2019. A female of Oxytate lobia sp. nov. was collected with a sweep net between shrubs in mixed forests during a seasonal spider survey and is described with measurements, morphological illustrations, and a diagnosis. The new species can be easily distinguished from similar species within the genus by the long copulatory duct conjugated with a spermatheca, a pair of triangular pits at the bottom, and no ditches.

Two linyphiid spiders, Saitonia kawaguchikonis Saito & Ono, 2001 and Asthenargus niphonius Saito & Ono, 2001 were confirmed from Korea for the first time. Males of S. kawaguchikonis and a female of A. niphonius were collected with pitfall traps in a leaf litter of mixed forests in three National Parks (Hallyeohaesang National Park, Mt. Naejangsan, and Mt. Sobaeksan) during the seasonal surveys for the spider fauna in mountainous terrain from 2018 to 2020. These two species were formerly known from China and Japan, or only from Japan, respectively. The present study describes these two species with measurements, morphological illustrations, and a distribution map. This report adds the genus Asthenargus Simon & Fage, 1922 from Korea to the Korean spider fauna for the first time.

Haplodrassus nojimai Kamura, 2007 of Gnaphosidae, which is only known in Japan was newly described in Korea with measurements and morphological illustrations. A female was collected from the levee of rice fields using a pitfall trap. The female epigynum has thick and remarkable transverse wrinkles and is densely covered with long blackish-gray hairs. The anterior hood was slightly rounded and the lateral margins were relatively short. The median septum was V-shaped with a broad base on the median part, and a pair of spermathecae was visible. The male is still unknown.

Four new species of the genus Alloclubionoides collected from mountain litter and hillock litter around the agricultural ecosystem of Korea are described in the present work with appropriate body measurements and morphological illustrations; A. hwaseongensis sp. nov., A. imi sp. nov., A. namhansanensis sp. nov. and A. nasuta sp. nov. Females of A. hwaseongensis sp. nov., A. namhansanensis sp. nov. and A. nasuta sp. nov. can be distinguished based on the epigyne shape and structure of internal genitalia from previously described species. Males of A. imi sp. nov. can also be distinguished based on the shapes of retrolateral tibial apophysis, embolus tip and conductor from previously described species. Also, a key to the Korean Alloclubionoides spiders is provided. Alloclubionoides gajiensis Seo, 2014 is newly synonymized with Alloclubionoides cochlea (Kim et al. 2007).

Spider community was surveyed at Nakdonggang River which is the longest river (525 km and 23,384 km2) located East-south part of Korea. Nakdonggang river is developing for water management and environmental conservation including restoration of river ecosystem under “The Four-River Restoration Project”. Sampling was made 3 occasions from June to August in 2009. Eight survey sites were selected from both sides of river in Andong, Sangju, Gumi and Seongju prefectures. Spiders were collected with sweep net for on the plants above ground and pitfall traps for on the ground. A total of 94 species of 71 genera in 24 families were identified from 805 collected spiders. Species richness was high in Salticidae (18 species, 19.1%), Araneidae (12 species, 12.8%), Lycosidae (9 species, 9.6%) in order. Wandering spiders (55 species occupied 58.5%, 493 individuals occupied 61.2%) were higher than webbing spiders (39 species occupied 41.5%, 493 individuals occupied 61.2%) in species richness and abundance. Dominant species were Tetragnatha praedonia (Tetragnathidae) and Neoscona adianta (Araneidae) in webbing spiders, and Anahita fauna (Ctenidae), Pirata procurvus (Lycosidae) and Gnaphosa kompirensis (Gnaphosidae) in wandering spiders with abundance. Collectively, most spiders collected from this study were water preferring spiders and showed different community structure compared to other reports from terrestrial spider fauna. Present result will bevaluable to compare the effect of development on the arthropod fauna after completion of the project.