Neptosternus haibini, Peng & Ji & Bian & Hájek, 2018

Peng, Yunfei, Ji, Lanzhu, Bian, Dongju & Hájek, Jiří, 2018, Description of Neptosternus haibini sp. nov. from China (Coleoptera: Dytiscidae: Laccophilinae), Zootaxa 4500 (4), pp. 581-586 : 582-584

Neptosternus haibini sp. nov.

( Figs 1, 3 )

Type locality. China, Guangdong Province, Shimentai National Nature Reserve , 113°18.4′E, 24°24.3′N, 155m.

Type material. Holotype, male (IAECAS), labelled: " China, Guangdong Province, Shimentai National Nature Reserve , 24°24'19''N, 113°18'22''E, 155m, 2017. 11. 24, Leg. Peng and Sun", " Holotype, Neptosternus haibini sp. n. " [red printed label] . Paratypes: 2 males (IAECAS), same label data as holotype ; 1 male (IAECAS): " China, Guangdong Province Yangchun, Bajia, Baishui Falls , 21°53'29''N, 111°21'49''E, 258 m, 2017. 11. 21, leg. Peng and Sun". All paratypes with the respective red printed paratype label .

Description of holotype. Habitus. Middle-sized, oval species, arched in lateral view. Dorsal and ventral surface shiny.

Colouration. Head dark brown, clypeus reddish brown; pronotum dark brown on disc, darker (brownish black) along anterior and posterior margins; elytra brownish black, each with yellowish markings arranged as follows: yellow transverse sub-basal band not reaching suture, two spots near elytral midlength (one small, almost imperceptible, round spot near suture, and one larger round spot near side of elytra) and one irregularly shaped subapical spot ( Fig. 1 ). Appendages ferruginous to yellowish brown; ventral surface reddish.

Surface sculpture. Head finely microreticulate, meshes polygonal, shallowly impressed; punctation consisting of few large punctures spread on surface; head with punctured depression along inner margin of eyes and another small transverse depression anteromedially of eyes.

Pronotum distinctly wrinkled laterally; microreticulation similar to that of head; punctation double: sparsely distributed small punctures–mostly in intersections of mesh-lines–and rather indistinct large punctures along anterior and posterior margins.

Elytra finely microreticulate, meshes transverse, shallowly impressed; punctation consisting of two kinds of punctures: small punctures distributed sparsely and irregularly–mostly in intersections of mesh-lines–and coarse large punctures forming a sutural, a discal and two lateral longitudinal rows.

Abdominal ventrites with fine microreticulation composed of polygonal meshes; ventrites III–V each with transverse row of setigerous punctures; ventrites IV–V each medially with one cluster of long and thick setae.

Male genitalia. Median lobe of aedeagus in ventro-lateral view slightly constricted in middle, broadest in distal fourth, then slightly attenuated in distal fifth to short pointed apex; inner margin straight in distal third ( Fig. 3 ).

Female. Unknown.

Measurements. Total length: 2.85–2.95 mm (holotype 2.90 mm); total length without head: 2.60–2.75 mm (holotype 2.60 mm); maximum width: 1.65–1.80 mm (holotype 1.75 mm).

Differential diagnosis. We compared the new species with N. wewalkai Balke, Hendrich & Yang, 1997 from northern Vietnam and Guangxi region in China. This species was described based on the female holotype from northern Vietnam ( Balke et al. 1997). Zhao et al. (2012) pointed out that specimens from Guangxi, including males, differ slightly in colouration from the type specimen, however considered this an intraspecific variability. They associated the Chinese specimens tentatively with N. wewalkai . We follow here the interpretation of Zhao et al. (2012).

In habitus and especially in dorsal surface colouration the new species and N. wewalkai are very similar. The only visible difference between them is the position of the yellow subapical spot on the elytra, which does not reach the side of the elytron in N. haibini sp. nov. ( Fig. 1 ), but is broadly connected with the side of the elytron in N. wewalkai ( Fig. 2 ).

The shape of the median lobes of N. haibini sp. nov. and N. wewalkai are clearly different: in ventro-lateral view—the median lobe of N. haibini sp. nov. is broadest in distal fourth, the inner margin is almost straight in apical third, and the apex is only shortly pointed ( Fig. 3 ). The median lobe of N. wewalkai is also broadest in distal fourth, but the inner margin is distinctly convex in apical third, and the apex is very elongate pointed ( Fig. 4 ).

Etymology. This species is named after Haibin Sun, a junior fellow apprentice of the corresponding author, who collected a part of the type specimens.

Habitat. Stream, ca. 1–2 m wide, with rocky steps and crystalline sand and coarse granitic gravel ( Fig. 5 ).

Distribution. So far known only from two localities in Guangdong province, China ( Fig. 6 ).

Figures

FIGURE 5. Habitat of Neptosternus haibini sp. nov. at the type locality (photo by Y. Peng).

FIGURE 6. Map of distribution of Neptosternus species in China. See Hendrich & Balke (1997) and Zhao et al. (2012) for previously published records of particular species.

FIGURES 1–4. 1–2. Habitus of Neptosternus; 3–4. Median lobe in ventro-lateral view (viewed at angle 45°). 1, 3. N. haibini sp. nov.; 2, 4. N. wewalkai.