Coelostoma (Lachnocoelostoma) bifidum, Jia, Fenglong, Aston, Paul & Fikáček, Martin, 2014

Jia, Fenglong, Aston, Paul & Fikáček, Martin, 2014, Review of the Chinese species of the genus Coelostoma Brullé, 1835 (Coleoptera: Hydrophilidae: Sphaeridiinae), Zootaxa 3887 (3), pp. 354-376 : 359-360

Coelostoma (Lachnocoelostoma) bifidum sp. nov.

( Figs. 1–6 , 9–10 , 20 )

Type material. HOLOTYPE: 1 male, JIANGXI, Jinggangshan, Shuangxikou, 03.x.2010, Fenglong Jia leg. [transcribed from Chinese] ( SYSU). PARATYPES: 38 spec. ( SYSU), same data as holotype [transcribed from Chinese]; 1 male, 3 spec. ( NMPC): Jingganshan Mts., Wankeng, stream valley, 26°31.8ʼN 114°11.8ʼN, 525 m, flood debris accumulated in the stream [MF15], 28.iv.2011, Fikáček, Hájek, Jia & Song leg.; 1 male, 16 spec. ( NMPC): Jinggangshan Mts., Baiyinhu env., 26°36.8ʼN 114°11.1ʼE, 800 m, drying-up stream in the stony bed, night collecting on the wet rocks with algae [MF01], 23-29.iv.2011, Fikáček, Hájek & Kubeček leg.; 4 spec. ( NMPC): Jingang Shan Mts., Baiyinhu vill. env., 26°36.8ʼN 114°11.1ʼE, 800 m, stream valley, wet rock, 23- 29.iv.2011, M. Fikáček & J. Hájek leg. GUANGDONG: 3 spec., Qingxin, 22.x.2004, Fenglong Jia leg. [transcribed from Chinese] ( SYSU); 1 male, 6 spec. ( NMPC): W of Qixing, Heishiding Nature Reserve, 23°27.9ʼN 111°54.3ʼE, 190-260 m, on wet rocks on side of waterfall—in crevicles and on the roots of the grasses growing on the rock [MF16], 1-3.v.2011, Fikáček, Hájek & Kubeček leg.; 17 spec., Shenzhen, Wutongshan, Hengmuling, 15.v.2011, Fenglong Jia leg. ( SYSU); 11 spec., Lianzhou, Dadongshan, 3.v.2006, Fenglong Jia leg. ( SYSU); 17 spec., Fengkai, Heishiding Nature Reserve, 2.v.2011, Fenglong Jia leg. GUANGXI: 21 males ( NMPC): Longsheng Hot Spring, forested river valley, 25°53.6ʼN 110°12.4ʼE, 360 m, hygropetric, wet rocks at side of the trail along the river, day and night collecting [MF09], 11-14.iv.2013, Fikáček, Hájek & Růžička leg. HONG KONG (11 spec.: PCPA, 3 males, 1 female; AFCD, 4 males, 3 females): 1 male, 1.v.2009, Shing Mun in stream, Paul Aston leg.; 1 male, 1.v.2009, Shing Mun in stream, Paul Aston leg.; 1 male, 29.x.2011 Shing Mun in river, Paul Aston leg.; 1 male, 15.xii.2012, Shing Mun in wet moss in water seep, Paul Aston leg.; 3 males, 3 females, Wutongzhai, 27.ix.2013, Fenglong Jia, Yingming Lee et Erich Chan leg.; 1 male, Lai Chi Wo, 25.ix.2013, Fenglong Jia, Yingming Lee et Eric Chan leg.

Diagnosis. Body length 4.7–5.2 mm. Prosternum moderately carinate throughout medial portion and forming a finger-shaped anteromedian spine. Pronotum with punctures slightly finer than on head and elytra; elytra with lateral portion more strongly punctate, without traces of series of punctures laterally. Mesofemora densely pubescent, except at extreme apex. First abdominal ventrite with a sharp carina reaching over basal half; last abdominal ventrite emarginate and with a row of stout setae apically. Aedeagus ( Fig. 20 ): 0.9 mm long. Median lobe narrowly and deeply emarginate at apex, gonopore situated at midlength; parameres as long as median lobe, truncate at apex.

Description. Form and Color. Body length 4.7–5.2 mm, width 3.0– 3.2 mm. Body oval, strongly convex. Dorsum black ( Figs. 1–2 ). Labrum, maxillary palpi, labial palpi yellowish to reddish brown, antennae yellowish to reddish brown with dark club. Ventral surface black with reddish pubescence. Femora and tibiae dark reddish brown, tarsi pale reddish.

Head. Surface with dense and moderately strong punctures. Intervals between punctures smooth, but with clear shagreen and transverse microsculpture on posterior margin (this part sometimes covered by pronotum). Clypeus truncate anteriorly. Eyes moderately sized, separated by ca. 5× the width of one eye, not emarginate anteriorly. Mentum with transverse microsculpture and strong punctures, strongly emarginate anteriorly and depressed on anterior half. Antennae with 9 antennomeres, antennal club loosely segmented. Maxillary palpomere 2 strongly swollen, palpomere 4 almost symmetrical, rather longer than palpomere 3. Gula very narrow, glabrous.

Thorax. Pronotum with slightly finer punctures than on head; anterior margin strongly bisinuate; posterior margin slightly bisinuate; lateral marginal bead reaching posterior corner, not continuing to posterior margin; posterior corner almost rectangular. Prosternum moderately carinate throughout medial portion, bearing strong finger-shape anteromedian spine. Mesoventrite with raised, arrowhead-shaped process, surface pubescent ( Fig. 6 ). Metaventrite with strongly raised median portion broadly projecting anteriorly between mesocoxae and abutted to mesoventral process ( Fig. 6 ); lateral portions of metaventrite densely pubescent, middle portion more shining, only sparsely pubescent. Metepisterna ca. 5× as long as wide, parallel-sided. Scutellar shield slightly longer than wide, with punctuation as on pronotum. Elytra with slightly coarser punctures than on pronotum, lateral and posterior punctures somewhat coarser than those on disc, without traces of series; sutural stria reaching basal half of elytra. Femora with deep tibial groove posteriorly. Mesofemora pubescent, except at extreme apex ( Fig. 9 ). Metafemora sparsely punctate, with dense microsculpture. Tarsi with long dorsal setae and gold ventral setae; metatarsi with fifth tarsomere almost as long as third and fourth combined. Claws moderately curved, with a pair of long setae beneath.

Abdomen. Abdominal ventrites densely pubescent. First abdominal ventrite with a sharp carina reaching over basal half; last ventrite emarginate and with a row of stout setae apically ( Fig. 10 ).

Aedeagus ( Fig. 20 ). 0.9 mm long. Median lobe subparallel in basal 0.6, slightly narrowed but still subparallel in apical 0.4, narrowly and rather deeply emarginate at apex (depth of emargination slightly variable in specimens examined), gonopore situate at midlength, wider than long; parameres as long as median lobe, truncate at apex, outer face slightly sinuate and distinct angulate apically, inner margin slightly bent and acutely produced apically.

Etymology. The species name is derived from the Latin bifidus, meaning bilobed, referring to the median lobe of aedeagus.

Biology. During the day, this species usually hides outside of water and may be collected e.g. from plant/grass roots at sides of a waterfall ( Fig. 4 , in this way specimens from Jiangxi: Jinggangshan and Guangdong: Shenzhen, Fengkai and Heishiding were collected), on large stones in rivers (from Guangdong: Qingxin), or in the moss on the wet rock (Dadongshan, Hong Kong). At night, the species may be found feeding on algal mats on wet rocks or ground at the edge of rivers ( Fig. 5 ). It was never collected at light.

Remark. This species is similar to C. coomani Orchymont, 1932 , C. lazarense Orchymont, 1925 and C. turnai Hebauer, 2006 . However, it is very easy to distinguish it from C. coomani by parameres sharply produced inwards apically, outer margin clearly angulate apically, median lobe with apical two-fifths clearly narrower than the basal part. It differs from C. lazarense by narrow and deeply emarginate median lobe apically, parameres angulate outwards apically. It differs from C. turnai by parameres sharply produced inwards apically, outer margin clearly angulate apically, median lobe not strongly broadened submedially, gonopore situated in middle length (basally in C. turnai ; Fig. 21 ).

Distribution. China (Jiangxi, Guangdong, Hong Kong).

Figures

FIGURES 1 – 8. Habitus, morphology and habitats of Chinese Coelostoma. 1 – 6: Coelostoma bifidum sp. nov. (1 – 2: habitus in dorsal and lateral views; 3: ventral morphology; 4: specimens hiding in grass root during the day (in Jiangxi: Jinggangshan), 5: active specimen of the surface of wet rock at night (in Guangdong: Heishiding); 6: detail of meso-metaventral elevation). 7: detail of pronotal and elytral punctation of C. hongkongense sp. nov.; 8: punctation of lateral portion of elytra of C. gentilii sp. nov.

FIGURES 9 – 14. Characters distinguishing the subgenera of Coelostoma occurring in China. 9 – 10: subgenus Lachnocoelostoma (C. bifidum sp. nov.); 11 – 12: subgenus Holocoelostoma (C. stultum); 13 – 14: subgenus Coelostoma s. str. (C. orbiculare). 9, 11, 13: mesofemur in ventral view; 10, 12, 14: posterior margin of andominal ventrite 5.

FIGURES 15 – 23. Aedeagus of Chinese Coelostoma. 15: C. fallaciosum, 16: C. vitalisi, 17 – 18: C. vividum (17: specimen from Guangdong: Heishiding; 18: paratype from Sumatra: Bengealis), 19: C. orbiculare, 20: C. bifidum sp. nov., 21: C. turnai (specimen from Hunan), 22: C. hajeki sp. nov., 23: C. hongkongene sp. nov.