Helochares densus Sharp 1890
Year: 2026
Type: article
Abstract: Helochares densus Sharp, 1890 (Figs 3A, B, 4A–F) Helochares densus Sharp, 1890: 352. Type locality: Sri Lanka (Kandy; Dikoya; Bogawantalawa). Helochares (Hydrobaticus) densus: Orchymont 1923: 9. Helochares (Hydrobaticus) tengchongensis Dong & Bian, 2021: 171. New synonym. Helochares guoi Yang & Jia, 2021: 59. New synonym. Material examined. 1 male (SYSU), Guangdong, Shenzhen, Dapeng Peninsula, Getian village, 22.48175°N, 114.52643°E, 2.VIII.2019, Fenglong Jia and Zuqi Mai leg. With red label “ Holotype Helochares guoi Yang, Jia sp. nov. ”. 35 spec. (SYSU), Guangdong, Shenzhen, Longhua District, Niuju Reservoir, in shallow stream, 22.5921°N, 114.0355°E, 100 m, 14.Ⅰ.2026, Zuqi Mai leg.; 8 spec. (SYSU), China, Yunnan, Xishuangbanna Tropical Botanical Garden, Lake near Wanglian Hotel, 21.9267°N, 101.2572°E, 450 m, 3.Ⅴ.2021, Zuqi Mai & Baoping Huang leg. Discussion. Helochares densus Sharp, 1890 is a typical Oriental species, widely distributed throughout Southeast Asia, ranging eastward from Sri Lanka to southeastern China. The species inhabits muddy banks of relatively open, still ponds and the margins of shallow streams, and is one of the most common species of the genus in southern China. This species can be readily distinguished from other morphologically similar species by the following combination of characters: small body size (2.9–4.8 mm in length); dorsum yellowish brown to greenish yellow, with elytral markings of varying shades that gradually fade during preservation (Fig. 3A, B); each elytron with 10 rows of punctate striae, interstices between striae with dense and coarse ground punctures (Fig. 3A); parameres (Prm in Fig. 4) of the aedeagus fused, forming an oval tunic (Tun in Fig. 4) surrounding median lobe (ML in Fig. 4); apex of parameres with a pair of stout, column-shaped projections (CSP in Fig. 4) ventrally, the orientation and angle of which may vary due to deformation of the parameres; median lobe usually constricted within the parameres (Fig. 4A–C), with basal apodemes (struts) (BA in Fig. 4) slightly longer than the main piece; main piece of median lobe consisting of four pairs of folded, spiny arms (subdivisions) (SA in Fig. 4) and a triangular median tube (MT in Fig. 4); when the median lobe is extended beyond the parameres, the unfolded spiny arms radiate outward (Fig. 4E, F). Helochares tengchongensis Dong & Bian, 2021 is an endemic species and is morphologically very similar to Helochares densus. However, this species was not compared with H. densus in its original description. We compared the original description and illustrations (Figs 9–12 in Dong & Bian 2021) of H. tengchongensis and also examined representative specimens of H. densus from southwestern Yunnan. The characters observed in H. tengchongensis fully match those of H. densus. Therefore, we confirm H. tengchongensis as a junior synonym of H. densus. Helochares guoi Yang & Jia, 2021 was described based on a single male from Guangdong of China, characterized by a seemingly unique aedeagus and the presence of fungal growth on one antenna. We examined the type specimen and found that it clearly belongs to Helochares densus. The apparently unusual structure of the median lobe of the aedeagus results from the extended position of median lobe (Fig. 4E, F). Accordingly, H. guoi is here regarded as another junior synonym of H. densus.
Authors: Mai, Zu-Qi, Jia, Feng-Long
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7167367129