Journal 
The genus Hydrovatus Motschulsky contains 206 described species worldwide (Nilsson, 2015) and 23 species in the Palaearctic region (Nilsson and Hájek, 2014). In East Asia, 11 species have been reported in China, seven species in Japan and four species in Taiwan. But only a single species is recorded in Korea (Nilsson and Hájek, 2014).
Members of Hydrovatus are characterized by the combination of the following features: apex of elytra and sternite VII acute; metacoxal process elongate and slender, and apical incison deep and narrow; gonocoxa fused into a knife-like structure with long lateral fringe (Miller and Bergsten, 2014).
In this paper, we report two species in the Korean fauna, one of which (H. acuminatus Motschulsky) is reported for the first time in Korea. Habitus, key and diagnostic characters with line drawings of the species are provided.
Materials and Methods
To identify Korean Hydrovatus species more reliably, we compared them with the type and voucher specimens in the Natural History Museum (NHM), London, United Kingdom. The specimens used in this study are deposited in Chungnam National University Insect Collection (CNUIC), Daejeon, Korea. We only present brief diagnoses of the species because previous researchers already described them in detail.
Taxonomic accounts
Family Dytiscidae Leach, 1815
Genus HydrovatusMotschulsky, 1853 점톨물방개속
HydrovatusMotschulsky, 1853: 4. Type species: Hyphydrus cuspidatusKunze, 1818.
See Biström (1996) for more detailed synonymies.
Key to the species of Korean Hydrovatus
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1. Antennomeres 7–10 slightly broad apically (Fig. 2A); apex of median lobe protruded and acute laterally ···················· ·································································· H. acuminatus
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- Antennomeres 7–10 distinctly broad apically (Fig. 3A); apex of median lobe rounded ······································H. subtilis
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Hydrovatus acuminatusMotschulsky, 1859
Hydrovatus acuminatusMotschulsky, 1859: 42.
See Biström (1996) for more detailed synonymies.
Diagnosis. Length 2.4–2.6 mm. Antennomere (Fig. 2A) 1 slender and longer than 2, 2–10 slightly broad apically and slightly longer than wide, 3–6 broad subapically in male, 11 long oval, widest at middle. Median lobe (Figs. 2B, 2C) of aedeagus broad and subparallel, apex protruded, acute laterally in dorsal view; slender and slightly curved, apex acute in lateral view. Paramere (Fig. 2D) semicircular, widest at base; apex rounded in lateral view.
Material examined. KOREA: Chungnam Prov.: 2♂♂, Taean-gun, Iwon-myoen, Gwan-ri, Iwon-seawall, N36°53′ 902″ E126°16′219″ 3 m, 5 VIII 2015, DH Lee, SH Lee, at light near reclaimed land; 2♂♂2♀♀, Taean-gun, Wonbuk-myeon, Hwangchon-ri, N36°51′855″ E126°11′973″ 13 m, 17 VII 2015, DH Lee, at light near abandon salt farm.
Distribution. Asia: Korea, China (Fujian, Guandong, Guangxi, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Xinjiang, Yunnan), Iran, Iraq, Israel, Japan, Nepal, Oman, Pakistan, Saudi Arabia, Syria, Taiwan, Turkey, Yemen (Socotra), North Africa: Egypt, Libya.
Hydrovatus subtilisSharp, 1882 점톨물방개
Hydrovatus subtilisSharp, 1882: 329; Nilsson, 1995: 36.
Hydrovatus adachii Kamiya, 1932: 4; Takizawa, 1933: 165.
See Biström (1996) for more detailed synonymies.
Published Korean records.Hydrovatus subtilis: Lee et al., 1992: 47; Kim et al., 1994: 133; Nilsson, 2003: 71; 2015: 41; Park et al., 2008: 220.
Diagnosis. Length 2.4–2.8 mm. Antennomere (Fig. 3A) 1 slender and longer than 2, 2–10 distinctly broad apically and slightly longer than wide in male, 11 long oval, widest at middle. Median lobe (Figs. 3B, 3C) of aedeagus narrowed apically, widest at basal fourth, apical margin broadly rounded in dorsal view; slender, slightly curved, apex vented and acute in lateral view. Paramere (Fig. 3D) semicircular, widest at basal fifth; apex acute in lateral view.
Material examined. Lectotype. 1♂ (NHM), with labels as follows: “Type, Siam, Sharp Coll 1905-313, Type ♂, Hydrovatus subtilis n. sp. Hydrovatus subtilis Sharp Des. O. Biström, 1989, Lectotype”. KOREA: Chungbuk Prov.: 1♀, Cheongju-si, Heungdeok-gu, Hyuam-dong, 7 Ⅴ 2005, D.-H. Lee, ex pond; 1♀, same data as former except for 1 Ⅵ 2005; 1♂, same data as former except for 15 Ⅹ 2005; 2♂♂8♀♀, same data as former except for 5 Ⅴ 2006 (2♂3♀♀, on slide); Gyeonggi Prov.: 1♀, Suwon-si, Seoho-pond, 14 Ⅸ 1990, SH Lee, ex pond; Gyeongnam Prov.: 1 ex, Sancheong-gun, Maetgol-pond, 7 VI 2009, SH Lee; Jeju Prov.: 1♀, Bukjeuju-gun, Jongdal-ri, 27 Ⅶ 1990, SH Lee, ex pond; 1♂, Namjeju-gun, Siheung-ri, 26 Ⅶ 1990, SH Lee, ex pond; Jeonnam Prov.: 1 ex, Jangseonggun, Songsan-pond, 1 VIII 2009, SH Lee; 1♂, Yeongam-gun, Taeganji, 22 Ⅶ 1989, SH Lee, ex pond.
Distribution. Korea, China (Macao), India, Indonesia, Japan, Laos, Malaysia, Taiwan, Thailand.
KSAE
