Coelostoma (Lachnocoelostoma) horni ( Régimbart, 1902 ), Regimbart, 1902

Jia, Fenglong, Aston, Paul & Fikáček, Martin, 2014, Review of the Chinese species of the genus Coelostoma Brullé, 1835 (Coleoptera: Hydrophilidae: Sphaeridiinae), Zootaxa 3887 (3), pp. 354-376 : 365

Coelostoma (Lachnocoelostoma) horni ( Régimbart, 1902)

( Fig. 31 )

Cyclonotum Horni Régimbart, 1902: 474 .

Coelostoma orbiculare f. Horni : Knisch, 1921: 77.

Coelostoma Horni : Knisch, 1924: 111 (specific rank confirmed). Coelostoma (Lachnocoelostoma) horni: Orchymont, 1940: 157 .

Type material: not examined.

Material examined. CHINA: YUNNAN: 1 male ( ASHC): Xishuangbanna, 20 km NW Jinghong, Man Dian vicinity, at light, 22°08ʹN 100°40ʹE, 740 m, 26.v.2008, A. Weigel leg. NEPAL: 1 male ( NMPC): prov. Narayani Saurana, bank of Rapti River, 180 m, 27°34ʹ80ʺN 84°29ʹ49ʺE, 18.iv.2000, A. Weigel lgt.

Diagnosis. Body size 4.5-5.0 mm. Prosternum finely carinate medially, with distinct dentiform process anteromedially. Head, pronotum and elytra with similar punctation; elytra with lateral portion not coarser punctate than dorsaly, without traces of series of punctures laterally. Mesofemora densely pubescent except at extreme apex. First abdominal ventrite with recognizable median carina basally; fifth ventrite emarginate and with a row of stout setae apically. Aedeagus ( Fig. 31 ). 0.6 mm long, widest at middle, Median lobe rather broad, with trilobed apex; gonopore situated apically; parameres much longer than median lobe, rather narrower than median lobe, strongly bent outwards medially, more or less curved on outer face subapically, apices truncate.

Biology. Unknown.

Occurrence in China. The occurrence of this species in China was originally reported by Orchymont (1925) ( Hong Kong). However, Orchymont (1935) did not list the species in his catalogue and noted, that “the Hong-kong specimens, of which three are in my cabinet, and alluded to in one of those notes, do not belong to horni . But as these three individuals are females an exact identification cannot be carried on without the males”. Wu (1937) followed Orchymont (1935), and did not list this species for China. In contrast, Mouchamps (1958) and Hansen (1999) listed C. horni from Hong Kong, likely based on the original record by Orchymont (1925). After examining extensive material of the genus Coelostoma from southern China including Hong Kong, we failed to find any representative of this species except the Yunnan one listed above. The locality of Xishuangbanna is situated in extreme southwest of China in lowlands close to the borders of Laos and Myanmar and already hosts the beetle fauna typical for true Southeast Asia (J. Hájek, pers. comm.). We thus suppose that Coelsotoma horni reaches China only in this extreme southwest and does not occur in the more eastern parts of South China. We hence consider the specimens from Hong Kong reported by Orchymont (1925) as C. horni as misidentified and actually belonging to another species. First reliable record of C. horni from China.

Taxonomic note. Coelostoma horni was originally described from Sri Lanka, and is nowadays considered as widely distributed both in Oriental Region (known from Malay Archipelago, continental southeast Asia and Indian subcontinent: Hansen 1999) and in Afrotropical Region (recorded from Arabian Peninsula, Mascarene Islands and South Africa: Hansen 1999). The genitalia of specimens from the Arabian Peninsula ( Yemen: deposited in NMPC, aedeagus figured by Fikáček et al. 2010) are indeed similar to the specimens of C. horni from the Oriental Region ( Fig. 31 illustrates the Chinese specimen, the examined Nepalese specimen has identical genitalia) in general shape. However, the aedeagus of the Arabian specimens is relatively larger and narrower (smaller and relatively wider in Oriental specimens), and its median lobe is only indistinctly widened apically (very distinctly widened in Oriental specimens). Based on these differences, we cannot exclude the possibility that the Arabian specimen are in fact not conspecific with true C. horni and represent an undescribed species. The identity of the African specimens remains unknown as none was studied by us.

Figures

FIGURES 24 – 31. Aedeagus of Chinese Coelostoma and related species. 24: C. coomani, 25: C. gentilii sp. nov., 26: C. phallicum, 27: C. huangi sp. nov., 28: C. martensi (paratype from Nepal), 29: C. wui, 30: C. vagum, 31: C. horni from southern Yunnan: Xishuangbanna).