Pachysternum nigrovittatum Motschulsky, 1863

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 : 34-38

Pachysternum nigrovittatum Motschulsky, 1863

( Figs. 1–3, 6–8 , 12, 15, 20, 22–25 , 28 , 32 , 46 , 62)

Pachysternum nigrovittatum Motschulsky, 1863: 447 .

Pachysternum nigrovittatum: Knisch (1921: 88, morphological note) ; Knisch (1924: 159, catalogue); Orchymont (1926a: 222, 227, identification key, notes on variation); Orchymont (1928: 84, catalogue); Satô (1979: 50, faunistics); Biswas & Mukopadhyay (1995: 154, faunistics); Hebauer (2000: 7, faunistics); Mukhopadhyay & Sengupta (2003: 38, faunistics); Hebauer & Ryndevich (2005: 50, faunistics); Mukhopadhyay (2007: 408, faunistics).

Megasternum nigrovittatum (Motschulsky) : Sharp (1890: 358).

Type locality. Sri Lanka, a mountain in the environs of Nuwara Eliya (“Montagne de Nura-Ellia”).

Type material. Lectotype (hereby designated): 1 female ( ZMUM): “[tiny red piece of paper] // [small rounded yellow label] // Type [small white label, in handwritten] // Pachysternum / nigrovittatum / Motsch. / Ind. or. Ceyl. M t. N. [yellow label, in handwritten]”. Paralectotype: 1 spec. [only head, prothorax and a mesothoracic leg preserved] (ZMUM): same label data as lectotype . On our request we have received two above mentioned specimens from the Motschulsky collection in ZMUM; both were glued on the same paper label. There is no indication of the number of syntypes in the original description, but the given type locality (“Montagne de Nura-Ellia et sur le continent indien”) indicates that Motschulsky (1863) examined also the specimens from other localities than Sri Lanka when describing the species. Therefore, some syntypes seem to be missing in his collection. In the present paper we are designating the complete specimen mentioned above as the lectotype, the remaining incomplete specimens as well as the remaining specimens not available to us have to be considered as paralectotypes.

Additional material examined. CHINA: Fujian: 48 spec. ( SYSU): Nanjing County, Hexi town [coordinates ca. 24°52'N 117°14'E], cow dung, 13.vii.2010, lgt. F. L. Jia. Guangdong: 1 spec. ( BMNH): Guangzhou , Baiyunshan [23°9'N 113°17'E], 27.ix.1980, lgt. P. M. Hammond; 17 spec., ( SYSU): Sanshui county, Lubao town [23°21'13''N, 112°53'46''E], 28.v.2004, lgt. F. L. Jia; 14 spec. ( SYSU): Gaoming county, Yangmei town, 23– 26.iv.2006, lgt. F.L. Jia; 1 spec. ( SYSU): Lianjiang County, Wuling, 29.ii.1985, lgt. Wu Wu ; 2 spec. ( SYSU): Xinyi County, 9.5.1986, lgt. Wu Wu; 13 spec. ( SYSU): Xinyi Cattle Farm, 7–13.vi.1986, lgt. Wu Wu ; 9 spec. ( SYSU): Guangzhou , Shipai Cattle Farm, 25.viii.1985, lgt. Wu Wu ; 4 spec. ( SYSU): Guangzhou , Henan Cattle Farm, 10.x.1985, lgt. Wu Wu . Guangxi: 5 spec. ( BMNH): Bama [24°10'14''N 107°14'56''E], i.1988, without collector; 5 spec. ( SYSU): Wuzhou, viii.1986, lgt. Wu Wu . Hainan : 1 female ( NHMW): 2 km S Mao’an, elev. 250 m [19°8'39.84''N 108°56'48.84''E], 20.i.1996, lgt. M. A. Jäch. Hong Kong: 4 spec. ( BMNH, NHMW): Hong Kong [ca. 22°24'N 114°8'E], without date, lgt. J. J. Walker; 4 spec. ( NHMW): New Territories, Luk Keng marsh near Kai Kuk Shue Ha [22°31'28''N 114°13'10''E], 14.i.1996, lgt. M. A. Jäch; 3 spec. ( NHMW): University Campus [= campus of the University of Hong Kong, ca. 22°17'N 114°8'E], 1996, lgt. G. de Rougemont. Zhejiang: 1 spec. ( BMNH): Chusan Is. [= Zhoushan , ca. 30°2'N, 122°7'E], without date, lgt. J. J. Walker. INDIA: Arunachal Pradesh: 1 female ( NMPC): 3.6 km NW Bhalukpong , elev. 280 m, 27°1'57''N 92°36'24''E, 7.v.2008, lgt. Fikáček , Podskalská , Šípek (16). Assam: 2 spec. ( BMNH): Sudiya [27°50'N 95°45'E], without date and collector. Goa: 6 spec. ( NMPC): 30 km S of Margao [= Madgaon ], Palolem env., elev. 0–30 m, 15°0'47''N 74°1'58''E, 4–12.viii.2002, lgt. P. Šípek & M. Fikáček . Karnataka: 1 spec. ( BMNH): Belgaum [15°51'N 74°33'0''E], without date, lgt. Andrewes & Bequest . Kerala: 1 spec. ( NHMW): 35 km NNE Trivandrum , Ponmudi , elev. 600 m [8°46'N 77°7'E], 2.i.1999, lgt. D. Boukal; 1 spec. ( BMNH): “ Malabar ” [without specified locality], without date and collector. Puducherry: 1 spec. ( FMNH): Karaikal, Kurumbagatam [10°55'N 79°49'E], ii.1947, lgt. Susai Nathan . Tamil Nadu: 3 spec. ( FMNH): Negapatam [= Nagappattinam , 10°46'N 79°50'E], without date, lgt. F. Psota; 40 spec. ( BMNH): Nilgiri Hills [without specified locality], without date, lgt. H. L. Andrewes; 2 spec. ( IRSNB): Shempagonur [= Shenbaganur , 6 km of Kodaikanal , ca. 10°14'N 77°30'E], without date and collector. Uttarakhand: 1 spec. ( BMNH): Akeswar , S Garhwal , Gauri Dutt . [29°48'N 78°37'E], 23.xi.1923, without collector; 2 spec. ( IRSNB): Dehradun, Dobhalwala [30°20'N 78°2'37''E], without date and collector; 6 spec. ( BMNH): W Almora , [ca. 29°36'N 79°34'E], without date, lgt. H. G. Champion. INDONESIA: East Nusa Tenggara: 5 spec. ( NMPC): Sumba , 20 km S of Waingapu , Wairinding [9°51'5''S 120°18'32''E], 30.i.–2.ii.2001, lgt. P. Votruba. North Sumatra: 1 spec. ( NHMW): Prapat [= Parapat ] env., elev. 1000 m [2°39'46''N 98°56'7''E], 17.ii.1990, lgt. S. Schödl. West Sumatra: 2 spec. ( BMNH): Fort de Kock [= Bukittinggi , 0°18'20''S 100°22'9''E], elev. 920 m, x.1922, lgt. E. Jacobson; 5 spec. ( IRSNB): same locality, 1925, lgt. E. Jacobson. LAOS: Bolikhamxai: 1 spec. ( NHMB): 70 km NEE Vientiane, elev. 150 m, 18°16'N, 103°11'E, 27– 30.iv.1997, lgt. V. Kubáň; 28 spec. ( NHMB, NMPC): 8 km NE Ban Nape, elev. 600 m, 18°21'N, 105°8'E, 1– 18.v.2001, lgt. V. Kubáň; 1 spec. ( FHGC): Ban Nape, Kaew Nua P. [18°18'7''N 105°4'24''E], 18.iv.–1.v.1998, lgt. E. Jendek & O. Šauša . Houaphan: 2 spec. ( NMPC): Phou Pane Mt. , elev. 1480–1510 m, 20°13'9''N 103°59'54''E, 1– 16.vi.2009, lgt. V. Kubáň. Louangphabang: 1 spec. ( NHMB): Thong Khan , elev. 750 m, 19°35'N 101°58'E, 11– 21.v.2002, lgt. V. Kubáň. Xiangkhouang: 2 spec. ( NMPC): Phou Sane Mt. , 30 km NE Phonsavan , elev. 1420 m, 19°38.2'N 103°20.2'E, 10–30.v.2009, lgt. V. Kubáň. MALAYSIA: Kedah: 3 spec. ( ASKC): Pulau Langkawi , environs of hotel Berjaya [= Pantai Kok village, 6°22'N, 99°40.5'E], 7–22.xi.2009, lgt. U. Schmidt. Melaka: 2 spec. ( BMNH): Malacca [2°11'53''N 102°14'59''E], without date, lgt. Wallace . Pahang: 1 spec. ( BMNH): Taman Negara [= Taman Negara National Park , ca. 4°41'N 102°34'E], 1–13.iii.1984, lgt. L. Jessop. Perak: 1 spec. ( BMNH): “ Perak ” [without specified locality], without date and collector. NEPAL: Gandaki: 1 spec. ( FHGC): Sikles Mts. , überh. Garlang , elev. 2000 m [28°19'N 84°0'E], 29.vii.1995, lgt. Fabrizi , Schmidt , Jäger . SINGAPORE: 8 spec. ( BMNH, IRSNB): Singapore [1°21'N 103°50'E], without date and collector. SRI LANKA: 2 spec. ( BMNH): “ Ceylon ” [without specified locality], without date and collector; 1 spec. ( IRSNB): same locality, without date, lgt. F. Chapuis. Sabaragamuwa: 1 spec. ( BMNH): Kitulgalle [= Kitulgala , 6°59'30''N 80°26'54''E], without date, lgt. C. Lewis. Uva: 1 spec. ( FHGC): 2 miles NW Haldummulla , elev. 1097 m [6°47'26''N 80°51'53''E], 2.iii.1962, lgt. Brinck , Anderson & Cederholm (111). Western Province: 5 spec. ( BMNH): Colombo [6°55'N 79°50'30''E], 14–15.xi.1915, lgt. M. Cameron; 1 spec. ( FHGC): lagoon 17 miles N of Colombo [ca. 6°45'N 79°54'E], 11.i.1962, lgt. Brinck , Anderson & Cederholm (8); 1 spec. ( FHGC): Yakkala, 18 miles NE Colombo [7°5'25''N 80°2'2''E], 15–21.i.1962, lgt. Brinck , Anderson & Cederholm (11). THAILAND: Uthai Thani: 1 spec. ( NHMW): 25 km NW Lan Sak , 240 km N of Bangkok [ca. 15°34'N 99°31'E], iii.1989, lgt. Thielen . VIETNAM: Bac Thai: 1 spec. ( NMPC): Tam Dao [ National Park , ca. 21°38'N, 105°30'E], without date, lgt. P. Marhoul. 1 spec. ( IRSNB): “ Tonkin, Foret de Kep ”, without date and collector. Gia Lai: 20 spec. ( NHMW): 40 km NW An Khe , Buon Luoi , elev. 620–750 m, 14°10'N 108°30'E, 28.iii.–12.iv.1995, lgt. Pacholátko & Dembický . Hoa Binh: 1 spec. ( IRSNB): “ Chobo ” [= Hoa Binh province, without precise locality], without date, lgt. H. Perrot; 1 spec. ( BMNH): Hoa Binh [ca. 20°50'N 105°20'E], viii.1918, lgt. R. V. de Salvaza; 36 spec., 1 male ( IRSNB): same locality, without date, lgt. A. de Cooman. Lam Dong: 1 spec. ( NHMW): Da Lat city [11°56'N 108°27'E], 27–21.iv.1994, lgt. Pacholátko & Dembický . Nghe An: 3 spec. ( BMNH): Lactho [= Lac Tho , 21°4'N 106°6'E], without date, lgt. de Cooman ; 66 spec. ( IRSNB): same locality, without date and collector.

Published records (not examined). INDIA: Andhra Pradesh: Kurnool district, Betamcherla; Prakasan district, Matur [= Martur] (both Mukhopadhyay 2007). Manipur: Andro, Imphal ( Mukhopadhyay & Sengupta 2004). Sikkim: Mongan ( Mukhopadhyay & Sengupta 2003). West Bengal: without detailed localities ( Mukhopadhyay 2007). LAOS: Loung Namtha: Louang Namtha env. ( Hebauer & Ryndevich 2005). THAILAND: Chiang Mai: Chiang Mai ( Hebauer & Ryndevich 2005).

Diagnosis. The species may be very easily distinguished from all remaining Asian Pachysternum by the combination of pale pronotum with large M-shape spot, elytra pale with at least some of elytral intervals 2–10 completely dark ( Fig. 62), and deeply bisinuate outer margin of anterior tibia ( Fig. 46 ). By the coloration of pronotum it resembles P. cardoni which is much larger and wider and never bears the combination of entirely pale elytral interval 2 and largely dark interval 4, and the apical portion of its median lobe is gradually narrowing apicad (narrow and nearly parallel-sided in P. nigrovittatum , Fig. 32 b). The elytral coloration of P. nigrovittatum may resemble pale specimens of P. sulawesicum , but may be easily distinguished from it by deeply bisinuate outer margin of anterior tibiae (continually arcuate in P. sulawesicum ) and distinctly narrowed apical portion of the median lobe (nearly parallel-sided throughout in P. sulawesicum ).

Redescription (based on specimens from Sri Lanka). Body elongate oval, shape of elytra sexually dimorphic, female with very distinctly pronounced humeral portion of elytra. Body length 2.2–3.0 mm (lectotype: 2.3 mm); body width 1.4–2.0 mm (lectotype 1.6 mm).

Coloration ( Fig. 62). Head brown widely pale reddish median portion of frons and transverse ridge. General coloration of pronotum pale reddish, bearing M-shaped black spot of variable extent, leaving wide lateral portions, anteromedian part and a pair of large posterior submedian parts reddish; posterior margin black. Elytra pale reddish brown, with alternating pale and black intervals as follows: interval 1 entirely black, interval 2 entirely pale, interval 3 pale except of short black portion in anterior third, interval 4 black in anterior four fifths, pale apically, interval 5 entirely pale, interval 6 similar to 4, but with short pale area subbasally, intervals 7–9 pale subbasally (forming pale humeral spot), otherwise black except for apical-most portion, Interval 10 (lateralmost one) pale. Ventral surface of head and prothorax reddish brown, meso- and metathorax dark brown, abdominal ventrites 1–4 largely pale reddish posteriorly, ventrite 5 entirely pale reddish. Legs pale reddish.

External morphology. Clypeus with fine and rather sparse punctation consisting of slightly semicircular punctures of two slightly different sizes separated by ca. 1–2× puncture width. Punctation of frons similar to that on clypeus, only with slightly larger punctures. Interstices on head without microsculpture. Larger punctures on pronotum semicircular, deeply impressed, much larger than small punctures; small punctures transverse, divided from each other by 2–3× puncture width. Pronotal interstices without microsculpture. Prosternum with distinct median carina. Elytral series consisting of large, shallow punctures; interval punctation with very fine semicircular punctures much smaller than serial ones, with sparsely intermixed slightly larger setiferous punctures of the same shape; interstices with weakly developed mesh-like 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 setiferous punctation, interstices without microsculpture; lateral portions with very coarse and dense, densely pubescent punctation. Anterior tibia rather narrow, outer margin deeply bisinuate, outer series of spines interrupted at the place of the sinuation.

Male genitalia ( Fig. 32 ). Tegmen 1.3–1.4 mm long, median lobe 1.3–1.4 mm long. Phallobase ca. 2× as long as parameres, basally slightly asymmetrical but without detached manubrium. Median lobe widest in basal third, weakly narrowing to apical third, narrow and nearly parallel-sided in apical third, apex rounded; gonopore subapical, rather indistinct; lateral pubescent lobes distinct only subapically. Sternite 9 narrow, without V-shaped apical emargination.

Variation. Rather variable species, with the variation concerning mainly the coloration, dorsal microsculpture, body size and slightly also the extent of sexual dimorphism in body shape. Pale specimens ( Fig. 62c) have largely reddish elytra with dark T-shape spot (consisting of dark elytral interval 1 and bark base of elytra) and dark spots at midlength of intervals 4 and 6–9 and subbasally on intervals 6–7. The extent of dark area is increasing in other specimens through the most typical coloration mentioned in the redescription ( Figs. 62a–b), to dark specimens with largely black elytra and very apparent reddish spots at bases and in apical portions of intervals 2, 3, 5 and 8– 10 and narrowly pale lateral margin of elytron ( Fig. 62g). The coloration of pronotum varies in the same extent, bearing a median and a pair of submedian dark spots in palest specimens ( Fig. 62c), the dark M-shaped spot in most specimens ( Figs. 62a–b, d–e) and a being largely dark at pronotal disc with only a weakly developed pale spots submedially in dark specimens ( Figs. 62f–g). Dorsal microsculpture usually consists of rather weak meshlike microsculpture which is often rather inconspicuous, but in extremely dark and/or small specimens the microsculpture is often very distinct. The body shape of males is constant in all specimens examined, but the shape of females may vary from rather short and wide specimens with weakly pronounced shoulders to very distinctly elongate specimens with highly pronounced shoulders and elytra strongly narrowing apicad (the most elongate females are known from the island of Sumba). The shape of the anterior tibia as well as of the male genitalia (including the median lobe and sternite 9) is very constant in all examined specimens irrespectively to their variation in the above characters, which we therefore consider as intraspecific.

Biology. Coprophagous species inhabiting excrements of various herbivorous mammals.

Distribution. Widespread throughout the Oriental Region from Nepal and Sri Lanka through India, whole continental SE Asia and some of the islands of Sundaland (Sumatra, Sumba). Records are surprisingly missing for whole lowland northern part of India (and P. nigrovittatum seems therefore be absent from semidesert areas) and from many islands of Sundaland (in this case most probably because of the collecting bias).

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 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.

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.