Pachysternum cardoni Orchymont, 1926

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 : 20-21

Pachysternum cardoni Orchymont, 1926

( Figs. 29 , 42 , 52)

Pachysternum cardoni Orchymont, 1926a: 220 .

Pachysternum cardoni: Orchymont (1928: 83, catalogue) ; Satô (1979: 49, faunistics); Biswas & Mukhopahyay (1995: 154, faunistics); Hebauer (2002b: 57, faunistics); Hansen (1999: 307, catalogue); Mukhopadhyay & Sengupta (2003: 38, faunistics); Hansen (2004: 66, catalogue).

Type locality. India, Barway [Mission] [= India, Chhattisgarh state, Jashpur district, Chainpur env., coordinates ca. 23°08'N 84°14'E]. The type locality was erroneously mentioned as “ India, Madhya Pradesh, Barwah” by Hansen (1999). The name Barway, even through missing from recent maps, refers to the name of the Mission led by Belgian Jesuits in the second half of 19th and at the beginning of 20th century, situated around the recent city of Chainpur (see the map by Tete 1984). Tete (1984) also mentions that Farther Cardon was the missionary in charge of the Barway region in 1890’s - this person is evidently the same as “R. P. Cardon” mentioned as a collector of the holotype by Orchymont (1926a).

Type material examined. Paratypes: 3 spec. ( IRSNB): “Gopaldhara / Br. Sikkim / H. Stevens // A. d’Orchymont det. / Pachysternum / Cardoni / d’Orchymont // Para- / type”. [Note. The holotype from “Barway” was not found in the Orchymont collection in IRSNB – it may be lost or was possibly returned to the collection of the Zoological Survey in Kolkata, India which would mean it is inaccessible and possibly damaged. As the original Orchymont’s understanding of this species is clear and not problematic, we refrain from designating the neotype at the moment] .

Additional material examined. CHINA: Anhui: 3 spec. ( NHMB, NMPC): Dabieshan , 65 km SW Huoshan, elev. 1400 m [30°51'N 116°2'E], 21–23.vi.1996, lgt. Bolm. Guangxi: 1 spec. ( NHMB): Miaoershan , S slope , elev. 1300–2000 m [ca. 25°50'N 110°30'E], 25–26.vi.1997, lgt. Bolm. Guizhou: 1 female ( NHMW): 30 km NW Jiangkou , Fanjing , Shan-Kuaichang , elev. 500 m, 27°54'23.34''N 108°41'55.31''E, 9.v.2000, without collector; 1 spec. ( NMPC): 60 km N Kaili, Shibing-Yuntai Shan, 27°7'25''N, 107°59'E, 21–25.v.1995, lgt. E. Jendek & O. Šauša . Hunan: 5 spec. ( NHMB, NMPC): Wulingyuan , Tianzishan nature reserve , elev. 800 m, 29°20'47''N, 110°32'17''E, 16–18.vi.1997, lgt. Bolm. Shandong: 1 spec. ( IRSNB): Kiautschau [= Jiaozhou, 36°16'N 120°2'E], without date and collector. Sichuan: 2 spec. ( NHMB): Mt. Emei , elev. 600–1050 m [29°33'N 103°22'E], 5–19.v.1989, lgt. L. Bocák; 1 male ( NMPC): “ Wassuland, Chunchwa , Szechuan ” [= Yingxiuwan env., 31°17'24''N 103°21'36''E], without date, lgt. Reitter . Yunnan: 1 male ( NHMW): 100 km W Baoshan, Gaoligong Shan nature reserve, 25°5'43.34''N 98°15'11.49''E, 14–21.vi.1993, lgt. E. Jendek & O. Šauša. INDIA: Arunachal Pradesh: 1 spec. ( BMNH): “ Burma, Mishmi hills” [currently in India, coordinates ca. 27°51'N, 96°34'E], 1935, lgt. M. Steele. Sikkim: 2 spec. ( FHGC, ASKC): Pemayangtse env., elev. 1900–2080 m, 27°18'16''N 88°15'10''E, 15–17.v.1998, lgt. Fabrizi & Ahrens . West Bengal: 11 spec. ( BMNH): Gopalghara [coordinates ca. 27°4'42''N 88°16'2''E], without date, lgt. H. Stevens. LAOS: Bolikhamxai: 1 spec. ( NHMB): 8 km NE Ban Nape, elev. 600 m, 18°21'N, 105°8'E, 1–18.v.2001, lgt. Pacholátko; 14 spec. ( NHMB, NMPC): same locality and date, lgt. V. Kubáň. Houaphan: 3 spec. ( NMPC): Phou Pane Mt. , 20°13ʹ09–19ʺN 103°59ʹ54ʺ–104°00ʹ0 3ʺ, 1–16.vi.2009, lgt. V. Kubáň. Louangphabang: 1 spec. ( NHMB): 5 km W of Ban Song Cha, elev. 1200 m, 20°33'N 102°14'E, 10–16.v.1999, lgt. V. Kubáň; 1 spec. ( NHMB): Thong Khan , elev. 750 m 19°35'N 101°58'E, 11–21.v.2002, lgt. V. Kubáň. Phongsali: 3 spec. ( NHMB): Phongsali env., elev. 1500 m, 21°41'N 102°6'E, 6–17.v.2004, lgt. V. Kubáň. NEPAL: Gandaki: 2 spec. ( FHGC): Kaski , Ghandruk , elev. 2200 m, 28°29'24''N 83°50'24''E, 25.iii.1994, lgt. Ahrens . THAILAND: Mae Hong Son: 1 female ( NHMW): Ban Huai Po , elev. 1700 m, 19°16'N, 97°56'E, 24–30.vi.1993, lgt. Schneider . VIETNAM: Bac Thai: 1 spec. ( NMPC): Tam Dao [ National Park , ca. 21°38'N, 105°30'E], without date, lgt. P. Marhoul. Hoa Binh: 1 unsexed specimen ( IRSNB): Hoa Binh [20°50'N, 105°20'E], without date, lgt. A. de Cooman.

Published records (not examined). INDIA: Chhattisgarh: “ Barway ” [= Jashpur district, Chainpur env., coordinates ca. 23°08'N 84°14'E], depository unknown (holotype) ( Orchymont 1926a). Sikkim: Mangan [precise localition not found], coll.? Zoological Survey of India ( Mukopadhyay & Sengupta 2003). West Bengal: Kalimpong env. [27°3'N 88°28'2 0''E], coll. NHMB ( Satô 1979). NEPAL: Gandaki: Manaslu Mts. , Dudh Pokhari Lekh , upp. Jorney vill., elev. 1900–2400 m [coordinates ca. 28°15'N 84°33'E], coll. Museum Erfurt ( Hebauer 2002b); Sikles Range , Kyojo Kharka N Sikles , N Pokhara , elev. 1850 m [coordinates ca. 28°23.5'N 84°7'E], coll. Museum Erfurt ( Hebauer 2002b).

Differential diagnosis. Pachysternum cardoni is rather easily recognizable by its large and widely oval body, weakly bisinuate outer margin of anterior tibiae, by the pale reddish coloration with large M-shape spot on pronotum (in most specimens) and longitudinal dark stripes along elytral series reaching subapically on series 2–4, and in most cases by rather distinct microsculpture of elytral interstices. However, the species varies rather widely in coloration and dorsal microsculpture, and darker specimens may resemble P. stevensi and P. kubani , which have both also very similar male genitalia. Pachysternum cardoni differs from both these species by clearly developed M-shaped dark spot on the pronotum leaving submedian parts of the pronotum behind midlegth pale (in dark specimens, the M-shape of the dark spot may be indistinct, but the pale submedian areas remain always distinct, Figs. 52e–f). In contrast, no pale submedian spots are developed in most P. kubani and in all P. stevensi ; in pale P. kubani , the dark spot is never M-shaped (for additional diagnostic characters, see couplets 3 and 13 in the key above). The pale coloration of the pronotum with the black M-shaped spot of P. cardoni also resembles the coloration of P. nigrovittatum ; see couplet 2 in the key above and P. nigrovittatum for diagnostic characters.

Redescription. Body widely oval, shape of elytra slightly sexually dimorphic, female with distinctly pronounced humeral portion of elytra. Body length 2.9–4.3 mm; body width 2.2–2.8 mm.

Coloration ( Fig. 52). Head dark brown with paler posterolateral corners of clypeus, median portion of frons and yellowish transverse ridge. General coloration of pronotum pale reddish, bearing a wide M-shaped black spot of variable extent, posterolateral corners black. Elytra pale reddish brown, with black stripes of variable extent along elytral series. Ventral surface of head reddish brown, thoracic sclerites dark brown, abdominal ventrites 1–4 largely pale reddish posteriorly, ventrite 5 entirely pale reddish. Legs pale reddish.

External morphology. Clypeus with moderately coarse but sparse punctation consisting of punctures of two different sizes separated by ca. 1–2× puncture diameter. Punctation of frons similar to that on clypeus. Interstices on head without microsculpture. Larger punctures on pronotum rounded, deeply impressed, much larger than small punctures; small punctures slightly scar-like, divided from each other by 2–3× 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 any trace of microsculpture. Elytral series 1 weakly impressed, lateral series distinctly impressed. Preepisternal elevation of mesothorax without posterolateral pits. Femoral lines on metaventrite indistinctly angulate, median portion of metaventrite bearing rather fine and sparse setiferous punctation, interstices without microsculpture; lateral portions with very coarse and dense, densely pubescent punctation. Anterior tibia rather narrow, outer margin slightly bisinuate, outer series of spines not interrupted at the place of the sinuation.

Male genitalia ( Fig. 29 ). Tegmen 1.6–1.7 mm long, median lobe 1.6–1.7 mm long. Phallobase 2.2× as long as parameres, bearing small, slightly asymmetrical but weakly detached basal manubrium. Median lobe widest at midlength, weakly narrowing apicad, apex narrowly rounded; gonopore subapical, rather indistinct; lateral pubescent lobes indistinct even subapically. Sternite 9 with deep V-shaped apical emargination.

Variation. Variable in the extent of the black spots on pronotum and especially elytra. Pronotal M-shaped spot may be slightly more or less expanded, but in all cases retains its M-like shape and leaves large submedian areas on the pronotum pale reddish. Elytral dark stripe along the punctate series vary from largely expanded and therefore completely or partly merging the adjacent stripes, to slightly darkening of elytral series not expanding to intervals at all and leaving the elytra nearly uniformly reddish. Microsculpture of elytra varies from totally absent even laterally to very clearly developed mesh-like microsculpture on lateral portion of the elytron.

Biology. Unknown.

Distribution. Widely distributed through NE India and Nepal, central and southern China and northern part of SE Asia. Recorded for the first time for Thailand and Vietnam. The unspecified records from the Chinese provinces Guizhou and Yunnan mentioned by Hansen (2004) were based on the above specimens from these regions.

Figures

FIGURES 29 – 32. Male genitalia of Asian Pachysternum (a: tegmen, b: median lobe, c: apical portionof median lobe, d: sternite 9). 29: P. c a rd o n i, 30: P. coomani, 31: P. haemorrhoum; 32: 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.