Pachysternum stevensi 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 : 42-44

Pachysternum stevensi Orchymont, 1926

( Figs. 34, 48, 68)

Pachysternum Stevensi Orchymont, 1926a: 220 .

Pachysternum stevensi: Orchymont (1928: 84, catalogue) ; Satô (1979: 50, faunistics); Biswas & Mukopadhyay (1995: 154, faunistics); Hansen (1999: 307, catalogue); Hebauer (2002b: 57, faunistics); Hansen (2004: 66, catalogue); Hebauer & Ryndevich (2005: 50, faunistics – based on incorrectly identified specimen of P. coomani ).

Pachysternum nigritum Jia, Wu & Pu, 1998: 125 . Syn. nov.

Pachysternum nigritum: Jia (1996: 91, unpublished English description) ; Hansen (1999: 307, catalogue); Hansen (2004: 66, catalogue).

Type localities. P. stevensi : India, Shempagonur [= Tamil Nadu: Shenbaganur, 6 km of Kodaikanal, coordinates ca. 10°14'N, 77°30'E]. P. nigritum : China, Guangdong province, Fengkai.

Type material examined. P. stevensi : Paratypes: 1 male, 1 female, 1 spec. ( BMNH, IRSNB): “ Gopaldhara / Br. Sikkim / H. Stevens // Andrewes / Bequest. / B.M. 1922–221 // A. d’Orchymont / Pachysternum / Stevensi / n. sp. / Cotype ”; 2 males ( IRSNB): “ Hoa Binh / Tonkin / de Cooman ”. [ Note. The holotype 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] .

P. nigritum : Holotype: male ( SYSU): “[Chinese text: China, Guangdong, Fengkai, 6.7.1986, lgt. Wu Wu ] / P. nigritus”. Allotype: female ( SYSU): same label data as the holotype. Paratypes: 1 male, 1 female ( NMPC), 38 spec. ( SYSU): same label data as the holotype; 1 male ( SYSU): “[Chinese text: China, Guangdong, Xinyi, 5.9.1986, lgt. Wu Wu ] / P. nigritus”; 1 male, 1 female, 34 spec. ( SYSU): “[Chinese text: China, Guangxi, Wuzhou, 8.1986, lgt. Wu Wu ] / P. nigritus”.

Additional material examined. CHINA: Fujian: 1 spec. ( IRSNB): Shaowu , Fukien , elev. 500 m [coordinates ca. 27°20'30''N 117°29'30''E], 30.x.1937, lgt. Klapperich ; 15 spec. ( SYSU): Nanjing County, Hexi town (cow dung), 13.vii.2010, lgt. F. L. Jia. Jiangxi: 6 spec ( SYSU): Jinggangshan Mts. , Jingzhushan , 26°31'N 114°05.9'E, 19.ix.2010, lgt. Shuang Zhao ; 109 spec. ( SYSU): same locality, 4.x.2010, lgt. Fenglong Jia; 5 spec. ( NMPC): same locality, 25.iv.2011, lgt. Fikáček , Hájek , Jia & Song ; 2 spec. ( NMPC): Jinggangshan Mts., Xiping , elev. 915 m, 26°33.7'N 114°12.2'E, lgt. Fikáček , Hájek , Jia & Song ; 1 spec. ( NMPC): Jinggangshan Mts. , Dabali env., elev. 1200 m, 26°29.3'N 114°08.1'E, lgt. Fikáček & Hájek . Guangdong: 1 male ( NMPC): Datian Ding Mt., elev. 1200– 1600 m, 22°16'N 111°13'E, 5–6.v.2002, lgt. Fencl ; 1 male, 4 spec. ( NMPC): same locality and collector, but 6.– 7.v.2002; 2 spec. ( SYSU): Xingning County, Luofu Mt. and Huangmaozhang Mt. , 2.vii.2004, lgt. F. L. Jia. Guangxi: 7 spec. ( NHMW): 10 km N Luizhou, 24°19'N 109°19'E, 10.xi.1993, lgt. H. Schillhammer (17a); 2 spec. ( BMNH): Bama [coordinates ca. 24°10'14''N 107°14'56''E], i.1988, without collector; 5 spec. ( HHCR): Guigang City, Mt. Zhanlongshan [29°5'24''N, 109°9'0''E], elev. 1140 m, 1–15.v.2009, lgt. Jingke Li. INDIA: Arunachal Pradesh: 1 spec. ( BMNH): “ Burma, Mishmi hills” [coordinates ca. 27°51'N 96°34'E, currently situated in India], 1935, lgt. M. Steele; 4 spec. ( BMNH): Dirang env, elev. 1700–1900 m, 27°21'N, 92°13'E, 8–22.v.2006, lgt. P. Pacholátko; 1 spec. ( BMNH): same locality and date, L. Dembický lgt. Meghalaya: 1 spec. ( NHMW): Garo Hills , Nokrek National Park , elev. 1150 m, 25°25'N 90°20'E, 13–22.xii.1997, lgt. V. Sinaev & M. Murzin. Sikkim: 1 spec. ( ASKC): Pemayangtse env., elev. 1900–2080 m, 27°18'16''N 88°15'10''E, 15–17.v.1998, lgt. Fabrizi & Ahrens . Tamil Nadu: 2 spec. ( NMPC): Nilgiri Hills , 11 km SE Kotagiri , elev. 1100 m, 11°24'N 76°56'E, 3– 15.v.2002, lgt. P. Pacholátko; 18 spec. ( NHMW, NMPC): Nilgiri Hills, Kunjappanai , elev. 900 m, 11°22'N, 76°56'E, 24.i.1999, lgt. D. S. Boukal (83). Uttarakhand : 8 spec. ( BMNH): W. Almora, [coordinates ca. 29°36'N 79°34'E], without date, lgt. H. G. Champion. LAOS: Houaphan: 1 spec. ( NMPC): Ban Salusi , Phu Phan Mt. , elev. 1500–2000 m, 20°15'N 104°2'E, 26.iv.–11.v.2001, lgt. J. Bezdĕk; 2 spec. ( NMPC): Phou Pane Mt. , 20°13ʹ09–19ʺN 103°59ʹ54ʺ–104°00ʹ0 3ʺ, 1–16.vi.2009, lgt. V. Kubáň. Xiangkhouang: 1 male, 1 spec. ( NMPC): Phou Sane Mt. , 30 km NE of Phonsavan , elev. 1420 m, 19°38.20ʹN 103°20.20ʹE, 10.–30.v.2009, lgt. V. Kubáň. NEPAL: Bagmati: 1 male ( NHMW): Godavari [coordinates 27°36'N 85°24'E], 3.vi.1996, lgt. Probst . Dhawalagiri: 1 male ( NHMW): Myagdi , Beni-Kusma , Gandaki-Khola , elev. 800–1000 m [coordinates ca. 28°14'N 83°41'E], 30.vi.1986, lgt. Probst ; 1 spec. (Erfurt): Kali Gandaki valley, Tatopani (= Bhurung ), elev. 1100–1400 m, 28°27'29''N 83°37'39''E, 14–17.vi.1986, lgt. C. Holzshuh; 2 spec. ( BMNH): Gandaki, Bakhri Kharka , elev. 1676 m [coordinates ca. 28°22'N 84°7'E], 24.iv.1954, lgt. J. Quinlan; 1 spec. ( FHGC): Buri Gandaki Maccha Khola village, elev. 870 m [coordinates ca. 28°13'N 84°52'E], 15.v.1996, lgt. Ahrens , Kulbe & Rulik ; 1 female ( NHMW): Gorkha, Lobubesi-Maccha Khola [coordinates ca. 28°10'N 24°53'E], 15.vi.1993, lgt. Probst ( N 15). Janakpur: 1 spec. ( FHGC): Ramechap , Bhandar , elev. 2000 m [coordinates ca. 27°34.6'N 86°20.6'E], 8.v.1997, lgt. W. Schawaller. VIETNAM: Bac Thai: 2 spec. ( NMPC): Tam Dao [ National Park , ca. 21°38'N, 105°30'E], without date, lgt. P. Marhoul. Gia Lai: 27 spec. ( NHMW, NMPC): 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: 4 spec. ( IRSNB): Hoa Binh [coordinates ca. 20°50'N, 105°20'E], without date, lgt. A. de Cooman. Lam Dong: 3 males ( NHMW): 12 km N of Dalat , Lang Bian , 11°55'N, 108°18'E, 28–30.iv.1994, lgt. Pacholátko & Dembický .

Published records. INDIA: Tamil Nadu: Shempagonur [= Shenbaganur , 6 km of Kodaikanal , coordinates ca. 10°14'N 77°30'E], depository unknown (holotype of P. stevensi ) ( Orchymont 1926a). West Bengal: Kalimpong env . [27°3'N 88°28'2 0''E], coll. NHMB ( Satô 1979) .

Differential diagnosis. Pale specimens of this species may be easily distinguished by the combination of uniformly dark pronotal disc with widely pale lateral margins, elytra with distinct subbasal pale spots on intervals 2– 5(-6), pale apical portion of elytra and slightly but distinctly bisinuate outer margin of anterior tibia ( Fig. 48 ). These specimens of P. stevensi may resemble dark specimens of P. cardoni (which may be distinguished mainly by larger and wider body form, pale median portion of frons and in some cases also by partly reduced microsculpture of elytra) and P. kubani (for diagnostic characters see couplet 12 of the identification key). Uniformly colored specimens of P. stevensi (i.e. those without clearly defined pale spots on elytra) are characterized by the combination of bisinuate outer margin of anterior tibia and strong microsculpture of elytra. These specimens may resemble P. rugosum by their coloration (outer margin of anterior tibia is continually arcuate in P. rugosum , bisinuate in P. s t e - vensi), P. coomani by the general coloration (outer margin of anterior tibia is continually arcuate in P. coomani which also has wide median lobe of the aedeagus nearly parallel-sided throughout, tibiae are bisinuate and the median lobe gradually narrowing apicad in P. stevensi ), and some morphotypes of P. a p i c a t u m (these may vary in the characters above, but their elytral interstices lack microsculpture, whereas microsculpture is very strong in P. stevensi ).

Redescription. Body widely oval, shape of elytra sexually dimorphic, female with distinctly pronounced humeral portion of elytra. Body length 2.1–3.3 mm; body width 1.4–2.1 mm.

Coloration. Head uniformly black, only with pale reddish transverse ridge. Pronotum black, with widely pale reddish lateral margins, pale area widest anteriorly, narrowest at posterolateral corner. General coloration of elytral black; interval 1 black throughout, intervals 2–5 with large vaguely defined pale reddish spots subbasally, apical third of elytra pale yellowish, lateral margin of elytron more or less pale throughout. Ventral surface of head dark brown, thoracic sclerites black, abdominal ventrites 1–4 reddish brown in posterior portion, entire ventrite 5 pale, legs pale reddish.

External morphology. Clypeus with moderately coarse dense punctation consisting of uniformly-sized rounded punctures separated from each other by ca. 1–2× puncture diameter. Punctation of frons similar to that on clypeus. Interstices on head without microsculpture. Larger punctures on pronotum rounded, shallow, much larger than small punctures; small punctures scar-like, 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 with strong 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 fine, moderately dense setiferous 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 slightly interrupted.

Male genitalia ( Fig. 34). Tegmen 1.2 mm long, median lobe 1.2 mm long. Phallobase 2× as long as parameres, bearing large, slightly to strongly asymmetrical and distinctly 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 or with moderately large V-shaped apical emargination (see Variation).

Variation. Dorsal coloration varies considerably in the distinctiveness of the elytral pale basal as well as apical spots. Typically, the basal spots merge in one triangular, more or less sharply delimited subbasal reddish spot and the elytral apex is yellowish ( Figs. 68a–f). In many specimens both basal and apical spots are more vaguely delimited and not so distinct, and in extreme cases the elytra are uniformly brown without any trace of paler spots (this extreme kind of coloration bear the types of P. nigritum examined, Fig. 68h). Similar variability concerns the pale areas on lateral margins of pronotum, but even in the specimens with uniformly colored elytra the sides of pronotum are still distinctly and rather widely paler, even though the pale spot is very vaguely delimited from the dark brown pronotal disc. Very apparent variation surprisingly concerns the shape of the median portion of male sternite 9, which may vary from deeply emarginated ( Fig. 34d) through shallowly emarginated to entirely rounded apically ( Fig. 34e). The shape varies even between the specimens from the same region (e.g., Guangdong province in China: the examined paratype of P. nigritum has entire, but the specimen from Datian Ding Mt. deeply emarginate median lobe of sternite 9) or in the specimens from the single collecting event (the sternite 9 varies from entirely rounded to deeply emarginate in specimens from Vietnam: Buon Luoi). The shape of the sternite 9 varies irrespectively to the coloration variability. As we failed to find any other morphological differences between the specimens with different shape of sternite 9 and as the intermediate shapes also occur, we consider this variation as intraspecific. No males were examined from the type locality in the Tamil Nadu state in India, but all dissected males from Kunjappanai (Nilgiri Hills) have deeply emarginate sternite 9.

Following the above variation patterns of P. stevensi , P. nigritum is clearly only a variation of P. stevensi without distinct spots and has to be therefore consider as a junior synonym of the latter species. Except of the difference in coloration and the shape of male sternite 9, both paratypes of P. nigritum completely correspond with other specimens of P. stevensi examined for this study.

Biology. A portion of the specimens examined were collected in cow excrements, no habitat data are provided for remaining material used for this study.

Distribution. Known from Himalaya, southern China and continental SE Asia (but not reaching Malayan peninsula). An isolated population seems to exist in southern India (Tamil Nadu), and no records are available from the rest of Indian subcontinent including the lowland northern India.

Figures

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.