Pachysternum kubani, Fikáček & Jia & Prokin, 2012

Fikáček, Martin, Jia, Fenglong & Prokin, Alexander, 2012, A review of the Asian species of the genus Pachysternum (Coleoptera: Hydrophilidae: Sphaeridiinae), Zootaxa 3219, pp. 1-53 : 31-34

Pachysternum kubani sp. nov.

( Figs. 27 , 33, 45, 60)

Type locality. Laos, Houaphan province, Mt. Phou Pane, Phongsali env., 20°13ʹ09–19ʺN 103°59ʹ54ʺ–104°00ʹ0 3ʺE, 1480–1510m.

Type material. Holotype: male ( NMPC): “LAOS-NE, Houa Phan prov. / 20°13ʹ09–19ʺN 103°59ʹ54ʺ- / 104°00ʹ0 3ʺE, 1480–1510m / PHOU PANE Mt., 1–16.vi. / 2009, Vít Kubáň leg. // Primary mountain forest / flight intercept trap / Laos 2009 Expedition / NHMB Basel / NMPC Prague”. Paratypes: 1 female, 1 spec. ( NMPC): same data as the holotype; 1 male, 1 female ( NMPC): “LAOS-NE, Xieng Khouang / prov., 19°38.20ʹN 103°20.20ʹE / Phonsavan (30 km NE): / PHOU SANE Mt., 1420m / 10.–30.v.2009, V. Kubáň lgt. // secondary mountain forest / flight intercept trap / Laos 2009 Expedition / NHMB Basel / NMPC Prague ”; 3 males, 2 females. ( NHMB, BMNH, NHMW): “ LAO, Phongsaly prov. / 21°41ʹN 102°6ʹE / PHONGSALY env. , / 6.–17.v.2004, ~ 1500m, / Vít Kubáň leg.”; 8 males, 12 spec. ( NMHB, BMNH, NMPC): “ LAOS, 1.–18.v.2001 / Bolikhamsai prov. / 18°21'N, 105°08'E / Ban Nape (8 km NE) / ~ 600 m, Vít Kubáň lgt.”; 1 male, 11 spec. ( NHMW, NMPC, SYSU, KSEM): “ China, Sichuan, Qingcheng Shan / 65 km NW Chengdu, 103.33E 30.53N / 18.v./ 3.–4.vi.1997, 8 km W Taiping / 800–1000 m, leg. A. Pütz ”.

Differential diagnosis. Pale specimens of Pachysternum kubani sp. nov. ( Figs. 60a–f) are easily recognizable from other Pachysternum species by pale yellowish elytra with irregularly lobate transverse dark stripe in anterior third ( Figs. 60a–e) or by very distinct pale humeral spots ( Fig. 60f), and distinctly bisinuate outer margin of anterior tibiae. By the coloration, these specimens may be confused with P. stevensi , from which they differ by the characters given in couplet 12 of the identification key. The body form of large specimens (and also the presence of pale spots on pronotal disc in pale specimens) resembles P. cardoni ; in contrast to it, the dark coloration of elytral series 2–4 reaches at most the midlength in pale specimens of P. kubani (it reaches subapically in P cardoni ), both species differ in the color pattern of the pronotum (with dark M-shaped spot or at least distinct pair of pale spots submedially in P. cardoni , with anteriorly trilobate dark spot or completely dark pronotal disc in P. kubani ) and the elytral microsculpture is also frequently different (absent in P. kubani , distinctly developed or rarely missing in P. c a rdoni). Dark specimens, which are usually slightly smaller than paler ones, highly resemble the mainland forms of P. apicatum (with which they sometimes even co-occur) in the coloration and very often also in the shape of anterior tibia; they may be distinguished from P. apicatum by the characters given in the couplet 15 of the identification key.

Description (based on the holotype). Body widely oval, shape of elytra slightly sexually dimorphic, female with distinctly pronounced humeral portion of elytra. Body length 2.2–3.5 mm (holotype: 3.3 mm); body width 1.6–2.2 mm (holotype 2.2 mm).

Coloration ( Fig. 60). Clypeus and lateral portions of frons black, transverse ridge between eyes and large median portion of the head pale reddish. Pronotum widely pale reddish along lateral and anterior margins, bearing large posteriorly wide and anteriorly trilobate black spot. General coloration of elytral yellowish; interval 1 black throughout, all elytral series black in anterior half, the black coloration slightly extending to intervals from series 2–5, but largely extending across intervals 6–11, forming large lateral black spot in anterior third of elytra. Ventral surface of head brown, mentum and thoracic sclerites black, abdominal ventrites dark brown anteriorly, largely pale reddish posteriorly. Legs brown, femora black.

External morphology. Clypeus with moderately coarse but rather sparse punctation consisting of rounded punctures of two slightly different sizes. Punctation of frons similar to that on clypeus, with punctures separated by 2–4× the puncture diameter. Interstices on head without microsculpture. Larger punctures on pronotum slightly crescent-like, deep, much larger than small punctures; small punctures slightly semicircular, divided from each other by ca. 1–1.5× puncture width. Pronotal interstices without microsculpture. Prosternum with very distinct median carina. Elytral series consisting of large, shallow punctures; interval punctation with rather fine semicircular punctures much smaller than serial ones, with sparsely intermixed slightly larger setiferous punctures of the same shape; interstices without microsculpture. Elytral series weakly impressed. Preepisternal elevation of mesothorax without posterolateral pits. Femoral lines on metaventrite indistinctly angulate, median portion of metaventrite bearing moderately coarse and dense punctation, interstices without microsculpture; lateral portions with very coarse and dense, densely pubescent punctation. Anterior tibia rather wide, outer margin distinctly bisinuate, outer series of spines interrupted at the place of emargination.

Male genitalia ( Fig. 33). Tegmen 1.3–1.5 mm long, median lobe 1.3–1.5 mm long. Phallobase 2× as long as parameres, bearing small, slightly asymmetrical, indistinctly detached basal manubrium. Median lobe rather narrow, widest in basal third, weakly narrowing apicad, apex narrowly rounded; gonopore subapical, rather indistinct; lateral pubescent lobes indistinct even subapically. Sternite 9 entire, rather narrow.

Variation. The species varies considerably in the extent of the black coloration on the head, pronotum and elytra. Coloration of the frons may vary from entirely dark brown to wide pale spot situated medially. Pronotum may bear large black spot which is wide posteriorly, but trilobate anteriorly, or may be completely black on the disc, with widely pale lateral margins (the pale areas widest anteriorly and narrowest posteriorly in that case) and median portion of anterior margin. Elytral coloration varies from largely reddish with irregular dark spots at anterior third of the elytral series ( Fig. 60c) through reddish with a more or less extended irregularly shaped transverse dark stripe at anterior third ( Figs. 60a–b, d–e) to largely dark brown to black with large to very small apical reddish spot and in some cases also basal pale spots ( Figs. 60f–i). The shape of the male sternite 9 varies from rounded (in the holotype and majority of the specimens examined; Fig. 33f) to shallowly emarginate (rarely found at the same localities where specimens with rounded apex of the sternite 9 predominate, Fig. 33g); a very deeply emarginate sternite 9 was found in a male from Xiangkhouang ( Fig. 33h) which also has extremely shortened tibial spines (all remaining specimens from the locality have usually developed sternite 9 as well as tibial spines, and the specimen is therefore considered as teratological here). This variation of the shape of the sternite 9 resembles that observed in P. stevensi , in which both rounded and emarginate forms are more frequent, however.

Etymology. The species is dedicated to my colleague Vítĕzslav Kubáň (NMPC) who collected most type specimens of this species.

Biology. Unknown. Most specimens were collected in primary or secondary mountain forests using flight intercept traps.

Distribution. Known from four localities in northern Laos (provinces Bolikhamsai, Houaphan, Phongsali and Xiangkhouang) and from central China (Sichuan).

Figures

FIGURES 26 – 28. Characters of male genitalia of possible phylogenetic significance (a: detail of apex, b: detail of basal struts). 26: median lobe of P. haemorrhoum; 27: median lobe of P. kubani; 28: apical portion of the aedeagus of P. nigrovittatum. Abbreviations: lr: lateral rim.