Coelostoma (Lachnocoelostoma) tangliangi, Jia, Fenglong, Lin, Renchao, Chan, Eric, Skale, Andre & Fikáček, Martin, 2017

Jia, Fenglong, Lin, Renchao, Chan, Eric, Skale, Andre & Fikáček, Martin, 2017, Two new species of Coelostoma Brullé, 1835 from China and additional faunistic records of the genus from the Oriental Region (Coleoptera: Hydrophilidae: Sphaeridiinae: Coelostomatini), Zootaxa 4232 (1), pp. 113-122 : 115-117

Coelostoma (Lachnocoelostoma) tangliangi sp. nov.

( Figs. 1–4 )

Type material. Holotype: male ( SYSU): China, Hainan Prov., Wuzhishan Mt., Reservoir Road , 18°53′N, 109°36′E, alt. 500m, 22.iv.2012, Feng & Dai lgt . Paratypes (15): 7 males, 5 females ( SYSU, NMW, NMPC, SHNU, CLSHU): same data as the holotype ; 2 males, 1 female ( SYSU): China, Hainan, Changjiang, Bawangling, Wang Jiliang & Gao Chao lgt., no other data.

Diagnosis. Body length 4.7–5.6 mm. Prosternum moderately elevated medially, very weakly carinate throughout medial portion and forming a finger-shaped anteromedian spine. Pronotum with punctures slightly finer than on head and elytra; elytra with lateral portions more strongly punctate, without traces of series of punctures laterally. Mesofemora densely pubescent except at extreme apex. First abdominal ventrite with a low carina basally; last abdominal ventrite slightly emarginate and with a row of stout setae apically. Aedeagus ( Figs 1–4 ) 1.15 mm long; median lobe strongly sclerotized, much shorter and wider than parameres, deeply excavated (horsesaddle-shaped), gonopore situated apically; parameres strongly widened in apical portion, truncate at apex.

This species can be easily separated from other species of the genus except of C. horni by the form of the aedeagus (median lobe much shorter than parameres, lobate apically, gonopore apical). It may be distinguished from C. horni ( Figs. 5–8 ) by ca. twice as large aedeagus with strongly sclerotized saddle-shaped median lobe.

Description. Form and Color. Body length 4.7–5.6 mm, width 3.1–3.2 mm. Body oval, strongly convex. Dorsum black. Labrum, maxillary palpi and labial palpi yellowish to reddish brown, antennae yellowish to reddish brown with dark club. Ventral surface black with reddish pubescence. Femora and tibiae dark reddish brown, tarsi pale reddish.

Head. Dorsal surface with dense and moderately strong punctures. Intervals between punctures smooth, but with clear shagreen and transverse microsculpture on posterior margin of head (this part sometimes covered by pronotum). Clypeus truncate anteriorly. Eyes moderately sized, separated by ca. 5× the width of one eye, not emarginate anteriorly. Mentum without transverse microsculpture posteriorly and strongly punctate posteriorly and laterally, strongly emarginate anteriorly and depressed on anterior half, without any punctures on depression. Antennae with 9 antennomeres, antennal club loosely segmented. Maxillary palpomere 2 strongly swollen, palpomere 4 almost symmetrical, rather longer than palpomere 3. Gula very narrow, glabrous.

Thorax. Pronotum with as fine punctures as those on head but sparser; anterior margin strongly bisinuate; posterior margin slightly bisinuate; lateral marginal bead reaching posterior corner, not continuing to posterior margin; posterior corner almost rectangular. Prosternum moderately elevated medially, very weakly carinate medially, bearing strong finger-shape anteromedian spine. Mesoventrite with raised, arrowhead-shaped process, surface pubescent. Metaventrite with strongly raised median portion broadly projecting anteriorly between mesocoxae and abutted to mesoventral process; lateral portions of metaventrite densely pubescent, middle portion more shining, only sparsely pubescent. Metepisterna ca. 5× as long as wide, parallel-sided. Scutellar shield slightly longer than wide, with punctation as on pronotum. Elytra with slightly coarser punctures than on pronotum, lateral and posterior punctures somewhat coarser than those on disc, without traces of punctural series; sutural stria reaching basal half of elytra. Femora with deep tibial groove posteriorly. Mesofemora pubescent except at extreme apex. Metafemora sparsely punctate, with dense microsculpture. Tarsi with long dorsal setae and gold ventral setae; metatarsi with fifth tarsomere almost as long as third and fourth combined. Claws moderately curved, with a pair of long setae beneath.

Abdomen. Abdominal ventrites densely pubescent. First abdominal ventrite with a low carina basally; last ventrite very weakly emarginate and with a row of stout setae apically.

Aedeagus ( Figs 1–4 ): 1.15 mm long. Median lobe strongly sclerotized, much shorter and wider than parameres, gradually widened towards apex, deeply excavated in lateral view, the excavation delimited by bilobed dorsal projection of median lobe and the dorsally bent apex of median lobe; gonopore situated apically. Parameres strongly widened in apical portion, truncate at apex, outer face sinuate in anterior third, apex rounded apically; inner margin strongly bent medially, truncate apically.

Etymology. The species is named after Mr. Tang Liang, a specialist of staphylinid beetles of Shanghai Normal University, who helped the first author a lot when checking specimens in SHNU.

Biology. Unknown.

Distribution. Only known from type locality.

Figures

FIGURES 1 – 14. Aedeagus of Coelostoma species. 1 – 4: C. tangliangi sp. nov., paratype; 5 – 8: C. horni from southern Yunnan: Xishuangbanna; 9: C. huangi from Vietnam: 6 km NE Lam Khan; 10: C. diversum, paratype from Sumatra: Panjinggahan; 11: C. jaechi sp. nov., paratype; 12 – 14: C. subditum (12 – 13: from Yunnan: Xishuangbanna; 14: from Hongkong). All figures except Fig. 13 to the same scale.