Coelostoma (Lachnocoelostoma) gentilii, Jia, Fenglong, Aston, Paul & Fikáček, Martin, 2014

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 : 366-367

Coelostoma (Lachnocoelostoma) gentilii sp. nov.

( Figs. 8 , 25 )

Type material. HOLOTYPE: 1 male, XIZANG, Zhangmu, Friendship Bridge, 1700m, 22.vi.1975, Fu-sheng Huang leg, IOZ(E)1358876. [transcribed from Chinese] ( IZCAS).

Diagnosis. Body length 4.3 mm. Prosternum moderately carinate medially, with a strong dentiform process anteromedially. Head, pronotum and elytra with similar punctation; elytra with lateral portion more or less strongly punctate and with distinct series of punctures laterally ( Fig. 8 ). Mesofemora densely pubescent, except at extreme apex. First abdominal ventrite with carina only at extreme base; fifth ventrite emarginate and with a row of stout setae apically. Aedeagus ( Fig. 25 ): 0.83 mm long. Median lobe slightly shorter than parameres, widely rounded at apex; gonopore situated at midlength; parameres slightly longer than median lobe, distinctly curved outside in apical fourth, and strongly expanded inwards to form an apical tooth.

Description. Form and Color. Body length 4.3 mm, width 3.0 mm. Body oval, strongly convex. Dorsum black, pronotal margins brown laterally. Labrum, maxillary 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 yellowish.

Head. Dorsal surface with dense and moderately strong punctures. Intervals between punctures smooth. Clypeus truncate anteriorly. Eyes of moderate size, separated by ca. 5× the width of one eye, not emarginate anteriorly. Mentum with transverse microsculpture and strong punctures, almost straight anteriorly and depressed anterior half. Antennae with 9 antennomeres, antennal club loosely segmented. Gula pubescent.

Thorax. Punctation of pronotum similar as on head; anterior margin strongly bisinuate; posterior margin slightly bisinuate; lateral marginal bead not overlapping posterolateral corner; posterolateral corner almost rectangular. Prosternum moderately carinate throughout medial portion, forming a sharp anteromedian spine. Mesoventrite with raised, arrowhead-shaped process, surface pubescent. Metaventrite with strongly raised median portion that broadly projects anteriorly between mesocoxae and meets mesoventral process; lateral portions of metaventrite densely pubescent, middle portion more shining, only sparsely pubescent. Metepisternum about 4.5× as long as wide, parallel-sided. Scutellar shield slightly longer than wide, with punctuation similar to that on pronotum. Elytra with punctuation similar to that on pronotum, laterally with distinct series of punctures coarser than ground punctation ( Fig. 8 ); elytral surface without shagreen; sutural stria reaching elytral midlength. Femora with deep tibial grooves posteriorly. Mesofemora densely pubescent, except at extreme apex. Metafemora sparsely punctate, with dense microsculpture. Tarsi with long dorsal setae and gold ventral setae; metatarsi with last 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 carina only at extreme base; last ventrite somewhat truncate, slightly emarginate.

Aedeagus ( Fig. 25 ). 0.83mm long. Median lobe rather wide, slightly shorter than parameres, almost truncate apically, gonopore situated at midlength, transversely oval; parameres slightly longer than median lobe, truncate apically, distinctly sinuate on outer face in apical fourth, strongly expanded inwards in form of an apical tooth.

Etymology. The new species is named in honour of Elio Gentili, an Italian hydrophilid specialist who has collaborated with the senior and third authors many times.

Biology. Unknown.

Remarks. This species may be distinguished from other species occurring in China and neighboring area especially by combination of moderately carinate prosternum forming a sharp anteromedian spine, the first abdominal ventrite with carina only at extreme base, elytra with distinct lateral series of punctures and the characteristic aedeagus. This species seems to be most similar to C. himalayanum Hebauer, 2002 , but can be distinguished by the morphology of the aedeagus. The new species has a wide and apically almost truncate median lobe (narrowly rounded in C. himalayanum ); parameres strongly expanded inwards to form an apical tooth (without projecting inner portion in C. himalayanum ). The shape of parameres is most similar to C. rubens Hebauer, 2002 , from which the new species differs by the gonopore situated at midlength (gonopore subapical in C. rubens ).

Distribution. Only known from type locality.

Figures

FIGURES 1 – 8. Habitus, morphology and habitats of Chinese Coelostoma. 1 – 6: Coelostoma bifidum sp. nov. (1 – 2: habitus in dorsal and lateral views; 3: ventral morphology; 4: specimens hiding in grass root during the day (in Jiangxi: Jinggangshan), 5: active specimen of the surface of wet rock at night (in Guangdong: Heishiding); 6: detail of meso-metaventral elevation). 7: detail of pronotal and elytral punctation of C. hongkongense sp. nov.; 8: punctation of lateral portion of elytra of C. gentilii sp. nov.

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).