Accepted by K. Williams: 9 Nov. 2018; published: 1 Feb. 2019 Licensed under a Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2019 Magnolia Press Zootaxa 4551 (3): 251–274 https://www.mapress.com/j/zt/ Article 251 https://doi.org/10.11646/zootaxa.4551.3.1 http://zoobank.org/urn:lsid:zoobank.org:pub:97EFCAB9-E174-4256-9FFC-E6F64C498E3F Descriptions of eight new species of the genus Parancistrocerus Bequaert (Hymenoptera: Vespidae: Eumeninae), with a key to the Oriental species TINGJING LI 1 & JAMES M. CARPENTER 2,3 1 Chongqing Key Laboratory of Vector Insects, Chongqing Key Laboratory of Animal Biology, Institute of Insect and Molecular Biol- ogy, Chongqing Normal University, Chongqing 401331, China. E-mail: ltjing1979@hotmail.com 2 Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA 3 Corresponding author. E-mail: carpente@amnh.org Abstract Eight new species, namely Parancistrocerus latitergus sp. nov. (China), P. lamnulus sp. nov. (China), P . laticlypeus sp. nov. (Thailand), P. prominens sp. nov. (Thailand), P. guangxiensis sp. nov. (China), P. discarinatus sp. nov. (Thailand), P. abyssicavus sp. nov. (Thailand), and P . similiandrocles sp. nov. (China) are described and illustrated. Parancistrocerus samarensis (von Schulthess, 1934) and P. incorruptus incorruptus Giordani Soika, 1972, are newly recorded from China and Thailand, respectively. An updated key to the Oriental species of the genus Parancistrocerus is also given. Key words: Hymenoptera, Eumeninae, Parancistrocerus, new species, China, Thailand Introduction The genus Parancistrocerus was established by Bequaert (1925) as a subgenus of Ancistrocerus, and presently contains 104 species and 22 subspecies, among which 46 species and 10 subspecies occur in the Oriental Region, one subspecies in both Oriental and Palaearctic Regions, 30 species and 10 subspecies in the Nearctic Region, 27 species in the Neotropical Region, and one species and one subspecies in both the Nearctic and Neotropical Regions (Girish Kumar et al. 2016; Carpenter unpublished). Giordani Soika (1994) systematically reviewed the Oriental species of the genus, including 29 species and nine subspecies. Thereafter, Gusenleitner (2000, 2002, 2003, 2007, 2011, 2012, 2013) fragmentarily reported some new species of Parancistrocerus from Vietnam, Thailand, Laos, and China (Hongkong, Taiwan), and Girish Kumar et al. (2016) found three new species from India. In our study of collections of the genus from China and Thailand, of which specimens from Thailand are deposited in American Museum of Natural History in New York, eight species are confirmed as new to science. Also, P. samarensis (von Schulthess, 1934) is newly recorded from China and P. incorruptus incorruptus Giordani Soika, 1972, is newly recorded from Thailand. In the present paper, these new species are described and illustrated in detail. Some related figures of these two new records are offered. Based on this research, an updated key to the Oriental species of the genus is also provided. Materials and methods The specimens examined are deposited in Chongqing Normal University (China), American Museum of Natural History (USA), and Queen Sirikit Botanic Garden (Thailand). Descriptions and measurements were made under a stereomicroscope (Nikon SMZ1500), and all figures were taken with Microptics-USA/Visionary Digital photomicrographic system developed by Roy Larimer and multiple layers stacked using Helicon Focus. The ratios used throughout the descriptions were measured in the same magnification of the stereomicroscope. All measurements were taken as the maximal length of body parts measured. Body length was measured from the