Pachysternum rugosum, 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 : 38-40

Pachysternum rugosum sp.nov.

( Figs. 10 , 14, 19 , 64)

Type locality. China, Gansu province, Lazikou valley, 34°09.9'N 103°51.9'E, 2120 m a.s.l.

Type material: Holotype: 1 female ( NMPC): “ CHINA: Gansu province / Lazikou valley, 2120 m, / 34°09.9'N 103°51.9'E / (GPS), 28.VI.2005 / J. Hájek, D. Král & / J. Růžička leg. (Ch 8) // baited pitfall traps (fish / meat + cheese); / vegetation along the / meadow on a bank of the / stream close to margin of / a mixed groove”. Paratypes: CHINA: Gansu Prov .: 1 female ( SYSU): same data as holotype; 1 female ( NMPC): “ CHINA: Gansu province / Lazikou valley, 2120–2510 m / 34°09.9–10.1'N 103°49.2–51.9'E / 28.VI.2005 / J. Hájek, D. Král & J. Růžička leg.”. Shaanxi Prov.: 1 female ( NHMW): “Central China / Mt. TAI BEN SHAN / SHAANXI province / 33 35 N, 107 43 E // H= 1300–1500m / 10.VIII–4.IX.1998 / leg. V. Murzin & V. Sinaev // Collection / Andreas Pütz / Eisenhüttenstadt ”.

Differential diagnosis. Ve ry easily recognizable from all other Oriental Pachysternum by the combination of large and wide body, continually arcuate outer margin of anterior tibia ( Fig. 47 ), lack of any pale spots on the head, pronotum and elytra ( Fig. 64), and very coarse punctation of dorsal body surface ( Fig. 14 ). It may resemble dark specimens of P. stevensi , which, however, differ by sinuate outer margin of the anterior tibia. By the large and wide body it resembles P. cardoni , which differs in the presence of pale spots on pronotum and elytra, slightly sinuate outer margin of anterior tibiae, and much finer punctation of pronotum and elytra.

Description. Body widely oval, female without pronounced humeral portion of elytra (males unknown, but sexual dimorphism in body shape probably absent). Body length 3.3–3.8 mm (holotype: 3.3 mm); body width 2.3– 2.6 mm (holotype 2.3 mm).

Coloration. Head black, only with slightly paler transverse ridge between clypeus and frons. Pronotum black, lateral margins vaguely paler, brown. Elytron slightly paler than pronotum, dark brown, with lateral and apical portions slightly paler than the disc; sharply delimited pale elytral spots absent. Ventral surface black, posterior portions of abdominal ventrites 1–4 and whole ventrite 5 brown. Femora dark brown, tibiae and tarsi brown.

External morphology. Clypeus with coarse and dense punctation consisting of uniform-sized closely punctures divided by interstices ca. as wide as puncture diameter. Frons with slightly coarser punctation than on clypeus, punctures nearly uniform-sized, divided by interstices much narrower than puncture diameter. Interstices on the head without microsculpture. Larger punctures on pronotum rounded, much larger than small punctures, small punctures nearly ring-like in shape. Pronotal interstices without microsculpture. Prosternum with rather indistinct median carina. Elytral series consisting of large, very shallow punctures; interval punctation consisting of rather large nearly ring-like punctures; all interval punctures of the same size, setiferous punctures as large as surrounding punctation; interstices without microsculpture mesally, with slightly developed microsculpture laterally. Elytral series indistinctly impressed, not very apparent. Preepisternal elevation of mesothorax without posterolateral pits. Femoral lines on metaventrite very distinctly angulate; median portion of metaventrite bearing large and dense punctation, interstices without microsculpture; lateral portions with very coarse and dense, densely pubescent punctation. Outer margin of anterior tibia continually arcuate, outer series of spines not interrupted.

Male genitalia. Unknown.

Variation. None observed.

Etymology. Rugosum (Latin) means shriveled, referring to the extremely coarse and dense punctation of the dorsal surface characteristic for this species.

Biology. The holotype and one paratype were collected in pitfall trap baited with fish meat and cheese.

Distribution. Known from the mountains in southern Gansu and southern Shaanxi in China.

Figures

FIGURES 1 – 11. General morphology of Asian Pachysternum. 1: mentum of P. nigrovittatum; 2: maxillary palpus of P. n i g ro - vittatum; 3: maxillary sucking disc of male of P. nigrovittatum; 4: head of P. curvatum, ventral view; 5: antenna of P. c u r v a t u m; 6 – 8: prothorax of P. nigrovittatum (6: posterior view, 7: lateral view, 8: ventral view); 9 – 11: prosternal plate (9: P. h a e m o rrhoum, 10: P. rugosum, 11: P, sulawesicum).

FIGURES 12 – 25. General morphology of the Asian Pachysternum. 12 – 14: pronotal punctation (12: P. nigrovittatum, 13: P. haemorrhoum, 14: P. r u g o s u m); 15: meso- and metathorax of P. nigrovittatum, ventral view; 16 – 19: preepisternal elevation of mesothorax (16: P. haemorrhoum, 17: P. s u l a w e s i c u m, 18: P. apicatum, 19: P. rugosum); 20 – 21: surface sculpture of metaventrite mesally and laterally of femoral line (20: P. nigrovittatum, 21: P. haemorrhoum); 22: elytral punctation of P. nigrovittatum; 23: scutellum of P. nigrovittatum; 24: anterior leg of P. nigrovittatum; 25: abdomen of P. nigrovitattum.

FIGURES 39 – 50. Anterior tibia of Asian Pachysternum species. 39: P. apicatum (a: lectotype, b: specimen from Borneo, Sabah); 40: P. c u r v a t u m, 41: P. sandacanum; 42: P. c a rd o n i; 43: P. coomani, 44: P. haemorrhoum, 45: P. kubani, 46: P. nigrovittatum, 47: P. rugosum, 48: P. stevensi, 49: P. s u l a w e s i c u m.