Neptosternus punctatus, Zhao, Shuang, Hájek, Jiří, Jia, Fenglong & Pang, Hong, 2012

Zhao, Shuang, Hájek, Jiří, Jia, Fenglong & Pang, Hong, 2012, A taxonomic review of the genus Neptosternus Sharp of China with the description of a new species (Coleoptera: Dytiscidae: Laccophilinae), Zootaxa 3478, pp. 205-212 : 206-207

Neptosternus punctatus sp. nov.

( Figs. 1 , 9 )

Type locality. China, Guangdong Prov., Dinghu Mt., ca. 23°10′N, 112°32′E.

Material examined. Holotype 3, labelled [transcription from Chinese]: “ China, Guangdong Province, Dinghu Mountain, 14. vi. 1963, Shaorong Chen leg. [handwritten]”, “ HOLOTYPE [red label, printed]”, “ Neptosternus punctatus sp. nov., det. Zhao, Hajek, Jia et Pang [printed]” ( SYSU). Paratypes: 5 exs., same label data as holotype, but “ PARATYPE [yellow label, printed]” instead of “ HOLOTYPE ” ( SYSU); 15 exs., same label data as holotype, but: “Tongxu Peng leg. [printed]” and the respective paratype label ( NMPC, SYSU).

Description of holotype. Large, broadly ovate species; body distinctly arched in lateral view. Shiny. TL: 3.5 mm; TL-h: 3.2 mm; TW: 2.2 mm.

Colouration. Head ferruginous to dark brown, clypeus yellowish brown; pronotum ferruginous to dark brown, darker along anterior and posterior margins; elytra ferruginous to brown-blackish with five bright orange spots arranged as follows: two basal spots, two median spots and one apical spot ( Fig. 1 ). Appendages ferruginous to orange; ventral surface reddish.

Surface sculpture. Head covered with fine microreticulation composed of shallowly impressed isodiametric meshes. Punctation double: small punctures between meshes almost imperceptible, sparse large punctures distributed on surface between eyes. Head with punctured groove along eyes and another small transverse groove anterolaterally of eyes. Reticulation of pronotum similar to that of head, but slightly more impressed; punctation similar to that of head, small punctures more distinct, large punctures confined to lines along anterior and posterior margin, and to longitudinal depressions along lateral margins. Reticulation of elytra composed of shallowly impressed slightly transverse polygonal meshes. Punctation of elytra distinctly double: densely distributed small punctures between meshes, and coarse large punctures forming four (sutural, discal and two lateral) longitudinal rows but also occurring in interstices, especially in first interstice and basal half of elytra. Prosternal process trifurcated, apically pointed and weakly darkened. Abdominal ventrites 3–5 each with row of setigerous punctures, broadly interrupted in midpart. Abdominal ventrite 5 medially with one long and thick seta. Ventral part with fine microreticulation composed of slightly transverse polygonal meshes; punctation fine and dense; submatt.

Male external genitalia. Median lobe of aedeagus in ventral view constricted in basal fifth, then broadened with sides nearly subparallel in apical third; apex obtuse ( Fig. 9 ).

Variability. Female without conspicuous external differences to male. Colouration of pronotum almost uniformly dark brown in some specimens. Measurements (N = 9). TL: 3.3–3.6 mm; TL-h: 3.1–3.4 mm; TW: 2.1–2.2 mm.

Differential diagnosis. With a body length reaching 3.5 mm and with a characteristic double punctation of elytra, Neptosternus punctatus sp. nov. is similar to Neptosternus latissimus Balke, Hendrich & Yang, 1997 , described based on two females from northern Vietnam. The new species differs from the latter in the slender habitus: TL-h/TW = 1.51–1.54 (1.42–1.44 in N. latissimus ), and the different pattern of basal pale spots on elytra: the elongate basal sutural spot in N. punctatus sp. nov. is always separated from the basal lateral spot which is extending laterally close to the lateral margin of the elytra ( Fig. 1 ) (the basal spots merge into the transverse basal band, which is never extended laterally in N. latissimus , Fig. 2 ).

Remark. Balke et al. (1997) characterised N. latissimus by the absence of a sutural puncture row on the elytra. However, the study of type specimens reveals that the sutural row is present (similar to that of N. punctatus sp. nov.), although much less distinct than the discal and lateral rows.

Etymology. Latin word for “punctured”, refers to the distinct elytral punctation of the new species. The specific epithet is an adjective.

Distribution. So far known only from the type locality in Guangdong province, China.

Figures

FIGURES 1 – 2. Habitus of Neptosternus. 1 — N. punctatus sp. nov. (paratype); 2 — N. latissimus (holotype). Scale bar = 1 mm.

FIGURES 9 – 13. Median lobe of aedeagus in ventral view. 9 — Neptosternus punctatus sp. nov.; 10 — N. wewalkai; 11 — N. hydaticoides; 12 — N. coomani; 13 — N. strnadi. Scale bar = 0.1 mm.