Coelostoma (Lachnocoelostoma) bannanicum Mai & Jia, 2022

Mai, Zuqi, Hu, Jian & Jia, Fenglong, 2022, Additional fauna of Coelostoma Brulle, 1835 from China, with re-establishment of Coelostoma sulcatum Pu, 1963 as a valid species (Coleoptera, Hydrophilidae, Sphaeridiinae), ZooKeys 1091, pp. 15-56 : 15

Coelostoma (Lachnocoelostoma) bannanicum Mai & Jia sp. nov.

Figure 1A-E

Type material examined.

Holotype: male (SYSU), China, Yunnan, Xishuangbanna Dai Autonomous Prefecture, Mengla County, Menglun Reservoir, 21°55'57"N, 101°11'25"E, 710 m, 5.vii.2016, Jiang, Liu, Huang & Liu leg. Paratypes: 4 spec. (SYSU), same data as the holotype.

Diagnosis.

Length 5.4-5.7 mm. Head, pronotum and elytra with similar punctation. Prosternal carina with a prominent tooth anteromedially. Elytra slightly parallel-sided in the middle, without serial punctures laterally. Mesofemora densely pubescent, except on extreme apex. First abdominal ventrite with distinct median carina on basal two-thirds. Fifth ventrite slightly emarginate and with a row of stout setae apically. Aedeagus (Fig. 1D, E ): 1.1 mm long. Median lobe slightly emarginated apically, slightly widened in the middle; gonopore situated subapically. Parameres longer than median lobe, strongly expanded and truncate at apex, outer apical angle rounded and inner apical angle nearly rectangular; apex of parameres wider than apex of median lobe.

Description.

Form and colour (Fig. 1A-C ). Total length 5.4-5.7 mm (holotype: 5.6 mm); maximum width 3.1-3.3 mm (holotype: 3.2 mm); body broadly oval, slightly parallel-sided in the middle, moderately convex. Dorsum black and shiny. Labrum, maxillary palpi and labial palpi reddish brown, antennae yellowish to reddish brown with dark club. Ventral surface reddish brown to black. Femora and tibiae dark reddish brown, tarsi pale reddish.

Head. Dorsal surface with dense fine punctures. Interstices between punctures smooth. Clypeus subtruncate anteriorly. Eyes of moderate size, distinctly emarginated anteriorly in lateral view, separated by ca. 3.6 × the width of one eye. Mentum strongly emarginate anteriorly and depressed in anterior half, with sparse punctures except on the depressed portion. Antennae with 9 antennomeres, antennal club (antennomeres 7-9) densely pubescent. Maxillary palpomere 2 strongly swollen, palpomere 4 truncate apically, slightly longer than palpomere 3. Gula narrow and glabrous.

Thorax. Pronotum widest posteriorly, gradually narrowed anteriad, with punctures as on head, anterolateral angles obtusely rounded, posterolateral angles blunt, anterior and lateral margins with narrow marginal bead. Prosternum with a carina medially and a prominent tooth anteromedially. Scutellum almost in shape of equilateral triangle, with punctures finer than those on pronotum. Elytra with more or less coarser punctures than those on pronotum, punctures on lateral and posterior portions somewhat coarser than those on disc; elytra without serial punctures; sutural stria reaching anterior third of elytra; lateral margin of elytra with bead but not explanate.

Legs. Pro- and mesofemora bearing dense pubescence, except on extreme apex. Metafemora not pubescent, with dense microsculptures and spares fine punctures. Meso- and Metatibiae slightly flattened, with strong apical spurs and series of sparse stout spines laterally. Tarsi with long dorsal setae and gold ventral setae; metatarsi with fifth tarsomere almost as long as third and fourth combined. Claws curved, with a pair of long setae beneath.

Abdomen. Abdominal ventrites densely pubescent. First ventrite with distinct median carina on basal two-thirds. Fifth ventrite with fine marginal bead and slightly emarginated apically, with a row of stout setae apically.

Male genitalia (Fig. 1D, E ). Aedeagus ca. 1.1 mm long. Median lobe slightly emarginated apically, widest in the middle, ca. 3.2 × as long as wide. Gonopore situated subapically, wider than long. Parameres longer than median lobe; outer face strongly sinuate at anterior third, strongly expanded and truncate at apex, outer apical angle rounded and inner apical angle nearly rectangular; apex of parameres wider than apex of median lobe.

Etymology.

This species is named after the type locality, Xishuangbanna Dai Autonomous Prefecture.

Biology.

On the basis of private communication to the collector, Dr. Ri-Xin Jiang (Guizhou University), the specimens were collected under stones at the edges of a mountain stream.

Remarks.

This species is very similar to C. coomani Orchymont, 1932 and C. jaechi Jia, Lin, Chan, Skale & Fikáček, 2017 in the weakly emarginate apex of the median lobe, and to C. surkhetensis Hebauer, 2002 in the shape of the median lobe. It can be distinguished from C. coomani ( Jia et al. 2014: fig. 24) by the gonopore situated subapically (Fig. 1D, E ) (situated at midlength in C. coomani ) and outer margin of parameres strongly sinuate subapically (Fig. 1D, E ) (not or only slightly sinuate in C. coomani ). It differs from C. jaechi ( Jia et al. 2017: fig. 11) by larger body size (body size <5 mm in C. jaechi ), median lobe widest at midlength (Fig. 1D, E ) (widest in apical third in C. jaechi ). It can be distinguished from C. surkhetensis (Fig. 8A-E ) by parameres strongly expanded apically (Fig. 1D, E ) (apex not expended in C. surkhetensis (Fig. 8D, E )), median lobe widest at midlength (Fig. 1D, E ) (outer face subparallel throughout in C. surkhetensis (Fig. 8D, E )).

Distribution.

Only known from type locality. China (Yunnan).

Figures

Figure 1. Coelostoma (Lachnocoelostoma) bannanicum Mai & Jia, sp. nov. A dorsal view B ventral view C lateral view D, E aedeagus (D dorsal view E ventral view). Scale bars: 1.0 mm (A-C); 0.5 mm (D, E).

Figure 8. Coelostoma (Lachnocoelostoma) surkhetensis Hebauer, 2002 A dorsal view B ventral view C lateral view D, E aedeagus D dorsal view E ventral view. Scale bars: 1.0 mm (A-C); 0.5 mm (D, E).