Coelostoma (Lachnocoelostoma) hongkongense, 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 : 364-365

publication ID	https://doi.org/ 10.11646/zootaxa.3887.3.4
publication LSID	lsid:zoobank.org:pub:ABD688ED-D7F6-40F1-8821-0C339293A2A5
DOI	https://doi.org/10.5281/zenodo.6140246
persistent identifier	https://treatment.plazi.org/id/297C0906-F210-FFBB-0CBA-857492C6E6EB
treatment provided by	Plazi
scientific name	Coelostoma (Lachnocoelostoma) hongkongense
status	sp. nov.

Treatment

Coelostoma (Lachnocoelostoma) hongkongense View in CoL sp. nov.

( Figs. 7 View FIGURES 1 – 8 , 23 View FIGURES 15 – 23 )

Type material examined. HOLOTYPE: male ( SYSU): HONG KONG, Shing Mun Country Park, night time, underside of stone in mud, close to dried moss, 10.ii.2009, Paul Aston leg. PARATYPES: 2 unsexed spec. ( PCPA), Hong Kong, Wu Kau Tang in wet moss 7.ii.2013, Paul Aston leg. 3 unsexed spec. ( PCPA), Hong Kong, Tai Po Kau in wet moss on overflowing river water tank 14.ii.13, Paul Aston leg. 1 male, 2 unsexed spec. ( PCPA, NMPC), Hong Kong, Tai Om Shan, Lam Tsuen valley in leaf litter in pristine stream, 18.ii.2013, Paul Aston leg.

Diagnosis. Body size 3.8 mm. Prosternum moderately carinate throughout medial portion, with dentiform process anteromedially. Head and pronotum with much finer and sparser punctation than on elytra, elytra with lateral portion more or less strongly punctate ( Fig. 7 View FIGURES 1 – 8 ), without traces of series of punctures laterally. Mesofemora densely pubescent, except at extreme apex. First abdominal ventrite not carinate; fifth ventrite emarginate and with a row of stout setae apically. Aedeagus ( Fig. 23 View FIGURES 15 – 23 ): 0.61mm long. Median lobe broadly rounded at apex, with small lateral tooth-like projections in apical third; gonopore situated at midlength; parameres as long as median lobe, broader than median lobe at apex, overlapping medial lobe, obtusely truncate apically, not projecting into sharp corner mesally.

Description. Form and Color. Length 3.8 mm, width 2.6 mm. Body oval, moderately convex. Head and elytra black, pronotum reddish brown to blackish, though all specimens show at least some red on the edges. Labrum, maxillary palpi, labial palpi, antennae yellowish to reddish brown, antennal club of same color as basal antennomeres. Ventral surface brown with reddish pubescence, abdomen yellow brown. Femora and tibiae dark reddish brown, tarsi color light.

Head. Surface with very fine and sparse punctures, intervals between punctures about 2.5-4.5× as wide as diameter of a puncture on disc, but somewhat denser posteriorly. 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, strongly emarginate anteriorly and depressed in anterior half. Antennae with 9 antennomeres, antennal club loosely segmented, apical segment longitudinally oval. Maxillary palpomere 2 strongly swollen, palpomere 4 slightly asymmetrical, slightly longer than palpomere 3. Gula very narrow, glabrous.

Thorax. Pronotum with similar punctuation as on head; anterior margin almost straight medially; posterior margin slightly bisinuate; lateral marginal bead reaching posterior corner, not overlapping to posterior margin; posterior corner almost rectangular. Prosternum moderately carinate throughout medial portion, with a dentiform process anteromedially. Mesoventrite with raised, arrowhead-shaped process, surface pubescent. Metaventrite with strongly raised median portion slightly projecting anteriorly between mesocoxae and abutted to mesoventral process; lateral portions of metaventrite densely pubescent, middle portion and posterior margin more shinning, only sparsely pubescent. Metepisterna ca. 5× as long as wide, parallel-sided. Scutellar shield slightly longer than wide, with punctation similar to that on pronotum. Elytra with punctures much coarser than those on pronotum ( Fig. 7 View FIGURES 1 – 8 ), lateral and posterior punctures somewhat coarser than those on disc, without traces of series; sutural stria fine, reaching basal 3/5 of elytra; with a row of punctures that is well defined and linear between the suture and sutural stria. Femora with deep tibial groove posteriorly. Mesofemora densely pubescent, except at extreme apex. Metafemora sparsely punctate, with dense microsculpture. Tarsi with pronounced 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 not carinite ( Fig. 3 View FIGURES 1 – 8 ); last ventrite more or less truncate, slightly emarginate.

Aedeagus. 0.61 mm long. Median lobe not reaching parameral apices, narrower than parameres in apical third, gradually narrowing from base to apex, with a distinct tooth on each side in apical third, apex widely rounded; gonopore circular, ca. longer than wide, situated at midlength of median lobe. Parameres longer than median lobe, overlapping median lobe, slightly widening towards apex, obtusely truncate apically, without projecting corners ( Fig. 23 View FIGURES 15 – 23 ).

Etymology. The species name is derived from Hong Kong where all type specimens were collected.

Biology. All specimens but one were taken in areas of very clean pristine water, all close to or in wet moss. A single specimen was found on the underside of a stone in the mud, close to the dried moss in the hottest and one of the driest Februaries ever recorded in Hong Kong.

Remarks. This species is the smallest representative of the genus in China. It can be easily distinguished from other known species from China by the combination of the following characters: small size, pronotum with much finer and sparser punctation than on elytra ( Fig. 7 View FIGURES 1 – 8 ), tarsi with pronounced dorsal setae, median lobe with distinct lateral projections ( Fig. 23 View FIGURES 15 – 23 ).