Eurystylus sauteri Poppius 1915

Eurystylus sauteri Poppius, 1915 (Figs 1I, 2I–L) Eurystylus sauteri Poppius 1915: 15; Yasunaga et al. 2017: 317 Eurystylus luteus Hsiao 1941: 247 (syn. by Yasunaga et al. 2017: 318). Diagnosis and description. See Yasunaga et al. (2017) for diagnosis and detailed description. Male genitalia: left paramere somewhat angled, its neck angled and projected frontally, hypophysis roundly truncated posteriorly (Fig. 2I); right paramere L-shaped, hypophysis with a small protuberance (Fig. 2J); endosoma membranous, with five noticeable sclerites; primary lobal sclerite (pl) almost straight, enlarged and hook-shaped apically; third lobal sclerite (tl) narrow; fourth lobal sclerite (fl) and median lobal sclerite (ml) broad and apically sharp; basal sclerotized teeth (bt) small near secondary gonopore (Fig. 2K–L). Biology. This species has been found on the flowers of various broad-leaved trees (Yasunaga et al. 2017). In Korea, both nymphs and adults have been collected from Rhus chinensis (Anacardiaceae), which is the first record of the host plant of this species. In Vietnam, the specimen was also collected from the flowers of a broad-leaved tree. Distribution. China, Japan, Korea, Taiwan, Vietnam (new record; Southern, Central Highlands). Material examined. [CNU] 1♀, Daesong-san (Mt), Pyongyang, North Korea (in label: Tesong-san bei Pjongjang, Korea), 5.vii.1974, M. Josifov; [CNU] 1♂, Pyongyang, North Korea (in label: Phjongjang Bof. Garten, Korea), 27.viii.1989, M. Josifov; [CNU] 1♂ 1♀, Donam-ri, Geumnam-myeon, Sejong-si, Geumgang arboretum, 28.vii.2014, on Rhus chinensis, J. Kim; [CNU] 2♂♂ 3♀♀, Gung-dong, Yuseong-gu, Daejeon, 1.vi.2015, by light trap, J. Kim.; [CNU] 1♂, Hoenggye-ri, Daegwanryeong-myeon, Pyeongchang-gun, Korea, by light trap, 29.vi.2016, J. Kim.; [CNU] 1♂ 1♀, Sanghyo-dong, Seoguipo-si, Jeju-do (Is.), Korea, 30.viii.2017, by light trap, J. Kim; [ZCDTU] 1♂, La Khuoi (14.2219°N, 107.9858°E, 650 m altitude), Chu Pah District, Gia Lai Province, Vietnam, 2.v.2025, J. Kim leg. (DTUHMM0067). Remarks. In the present study, we identified this species based on the examination of male genital characters (Fig. 2I–K), which confirms its occurrence in southern Vietnam and thereby extends the known southern limit of its distribution. Notably, Yasunaga et al. (2017) synonymized E. luteus Hsiao, 1941, previously recorded from Korea, with this species. Our examination of specimens collected from North Korea (by M. Josifov) revealed identical genital structures, supporting this taxonomic treatment (Fig. 2L). Furthermore, this species is distributed throughout the Korean Peninsula, including Jeju Island. Genetic analysis of the cytochrome c oxidase subunit I (COI) gene from populations collected across Korea – from Jeju Island to Gangwon-do near the northern border – revealed identical sequences. Some of these sequences have been published in public databases such as NCBI. Although COI sequences from the Vietnamese and North Korean populations were not available, the morphological uniformity and geographic continuity suggest, though do not definitively confirm, that these populations belong to the same species. Given the species’ broad host plant range and its ecological adaptability across both lowland and highland habitats, it is plausible that its actual distribution extends across much of the Indochinese Peninsula. Our findings therefore support the taxonomic treatment proposed by Yasunaga et al. (2017), while also highlighting the species’ potential for a much wider distribution than previously recognized.