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

Figures 3A-E , 12B

Type material examined.

Holotype: male (SYSU), China, Yunnan, Dehong Dai and Jingpo Autonomous Prefecture, Yingjiang County, Xima Town (昔马镇), Hulukou (葫芦口), Xingyun Secondary power station (星云二级电站), 1000 m, vi.2019, light trap, Zhao-yang Tang leg. Paratypes: 2 females (SYSU), same data as the holotype.

Diagnosis.

Length 4.4-4.6 mm. Head and pronotum with similar punctation. Prosternum carinate medially, with a prominent tooth anteromedially. Elytra not parallel-sided in the middle, each elytron with 10 distinct rows of serial punctures; intervals between series with two sizes of punctures especially in posterior half of elytron, all finer than those of the series, the finer punctures finer and shallower than the coarser punctures but not extremely so (Fig. 12B ); lateral margin of elytra with bead but not explanate. Mesofemora densely pubescent, except on extreme apex. First abdominal ventrite with carina on basal two-thirds. Fifth ventrite slightly emarginate and with a row of stout setae apically. Aedeagus (Fig. 3D, E ): 1.1 mm long. Median lobe widest basally, almost truncate apically, outer face nearly parallel-sided throughout; gonopore situated subapically, rounded, almost as wide as long. Parameres almost the same length as median lobe, outer face continually curved, apex of paramere pointed, curved inwards.

Description.

Form and colour (Fig. 3A-C ). Total length 4.4-4.6 mm (holotype: 4.5 mm); maximum width 2.6-2.7 mm (holotype: 2.7 mm); body broadly oval, not parallel-sided in the middle, moderately convex. Dorsum black to reddish brown, with lateral margin of pronotum and elytra slightly paler. Labrum, maxillary palpi and labial palpi reddish brown, antennae yellowish to reddish brown with dark club. Ventral surface reddish brown. 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, slightly emarginated anteriorly in lateral view, separated by ca. 4.2 × the width of one eye. Mentum emarginated anteriorly and depressed in anterior half, with sparse punctures and transverse microsculpture. 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 slightly sparser than those 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 in shape of equilateral triangle, with punctures as on pronotum. Each elytron with ten distinct rows of serial punctures; intervals between series with two sizes of punctures especially in posterior half of elytron, all finer than those of the series, the finer punctures finer and shallower than the coarser punctures but not extremely so (Fig. 12B ); series 1-4 only visible in posterior half of elytron, series 1 overlaps with sutural stria, series 3 and 4 fused together subposteriorly; series 5-10 nearly reaching elytral base, slightly sulcate posteriorly. The outer four serial punctures coarser and stronger than the inner six serial punctures (Fig. 12B ). 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 Metatibia 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 slightly emarginate and with fine marginal bead, with a row of stout setae apically.

Male genitalia (Fig. 3D, E ). Aedeagus ca. 1.1 mm long. Median lobe widest basally, ca. 3.9 × as long as wide, almost truncate apically, outer face nearly parallel-sided throughout; gonopore situated subapically, rounded, almost as wide as long. Parameres almost the same length as median lobe, outer face continually curved, apex of paramere pointed, curved inwards.

Etymology.

This new species is derived from the Latin adjective fortuna, fortunate, meaning the senior author was lucky to collect the new species.

Biology.

All specimens were collected in a light trap

Remarks.

This species also with ten rows of serial punctures on elytra as C. dactylopunctum sp. nov. It can be distinguished from the latter by apex of median lobe truncate and not emarginate (Fig. 3D, E ) (slightly emarginate and rounded apically in C. dactylopunctum sp. nov. (Fig. 2D, E )), apex of paramere pointed (Fig. 3D, E ) (paramere broadly truncate apically in C. dactylopunctum sp. nov. (Fig. 2D, E )), first ventrite with median carina on basal two-thirds (with complete median carina in C. dactylopunctum sp. nov.).

Distribution.

Only known from type locality. China (Yunnan).

Figures

Figure 2. Coelostoma (Lachnocoelostoma) dactylopunctum 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 3. Coelostoma (Lachnocoelostoma) fortunum 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 12. Lateral view of Coelostoma spp. (the red figures indicate the serial number of elytral serial punctures; the white arrows indicate the punctures of series; the circles indicate the coarser punctures; the squares indicate the finer punctures) A Coelostoma dactylopunctum sp. nov. B Coelostoma fortunum sp. nov. Scale bar: 1 mm (A, B).