Dactylosternum latum Fikacek et al. 2015
Creators: name: Mai, Zuqi
name: Hu, Jian
name: Minoshima, Yûsuke N.
name: Jia, Fenglong
name: Fikáček, Martin
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydrophilidae
Dactylosternum
Dactylosternum latum

description: Dactylosternum latum (Sharp, 1873)
(Figs. 9, 30–38, 54, 58, 62)
Cyclonotum latum Sharp, 1873: 64. Type locality: Japan, Kyushu, Nagasaki.
Coelostoma latum (Sharp): Zaitzev (1908: 403).
Dactylosternum latum (Sharp): Orchymont (1919: 108).
Dactylosternum Vitalisi Orchymont, 1925: 271. Type locality: Laos, Ban Sai. New synonym.
Type material examined: Dactylosternum latum: SYNTYPES: 1 male (BMNH): “ Japan / Lewis // Sharp Coll / 1905–313 // Type // Cyclonotum latum / type D.S. // SYNTYPE / CYCLONOTUM / latum Sharp, 1873 / YN Minoshima det. 2021” (Figs 32, 34); 1 male (BMNH), “ Japan / G. Lewis / 1910—320 // Cyclonotum / latum / mihi D.S. // SYNTYPE / CYCLONOTUM / latum Sharp, 1873 / YN Minoshima det. 2021”.
Dactylosternum vitalisi: HOLOTYPE: male (IRSNB): “ Laos: / Ban Sai / 8.12.1918 / Vitalis // Ban Sai / 8- XII-18 / No 2199 // TYPE // TYPE // A. d´Orchymont det. / Dactylosternum 1922 / Vitalisi d´Orchymont ” (Fig. 36); PARATYPE: 1 male (BMNH): “Fokien // A.d’ Orchymont det / Dactylosternum 1922 / Vitalisi d’ Orchymont // Co-type // co- TYPE.”
Note. On the request of loan of the type specimens of D. latum, we received two Japanese specimens of Sharp collection from BMNH. Sharp (1873) mentioned that he examined two specimens, therefore they can be considered as syntypes. Both specimens are male, morphologically identical and with labels indicating that they are from Japan. The syntype status of both specimens does not cause any taxonomic confusion and we hence retain their status of syntypes.
Additional material examined. CHINA: Anhui: 1 female (SYSU), Huangshan Prefecture, Tangkou County, Hougu, 13.VII.2013, Qiu & Xu leg.; Guangxi: 1male (HBUM), Tianlin County, Jiudongpin, 1200–1300m, 27.V.2002, Xiujuan Yang leg.; Hunan: 2 males, 1 female (HBUM), Shimen County, Huping Mountain, 17–20.VIII.2004, Jianfeng Wang & Jiliang Wang leg.; 2 females (SYSU), Shimen County, Huping Mountain, Maozhuhe, 6.VI.2017, Qiu & Xu leg.; 1 male (HBUM), Fenghuang County, Liangtouyang, 30.VII.2004, Jishan Xu & Lingxiao Chang leg.; Yunnan: 1 male, 1 female (SYSU), Baoshan Prefecture, Gaoligong Natural Park, 24.91°N 98.81°E, 1751 m, 22.V.2016, Yudan Tang & Ruijuan Zhang. Locality uncertain: 1 female (BMNH), “China. // Sharp Coll. / 1905- 313.” [Note: Precise identification of the species without examination of aedeagus is difficult, but the specimen agrees with the type specimens in all external characters.]
Diagnosis. Length 6.9–8.0 mm. Body oval, anterior half of elytra nearly parallel-sided (Fig. 9), moderately convex. Dorsal black, surface with fine punctures, comparatively shiny.Anterior margin of clypeus without marginal rim. Antenna yellow-brown, club compact. Elytra with sutural stria and ten distinct rows of serial punctures, all nearly reaching elytral base. Anteromedial portion of metaventral process with a strongly depressed pit (Fig. 58). Posterior margin of abdominal ventrite 5 with fine marginal bead, without stria behind the marginal bead (Fig. 62). Aedeagus (Figs. 30–38). Morphologically variable, phallobase shorter than parameres. Parameres slightly sinuate on outer margin. Median lobe widest in the basal one-fourths or at midlength, a little shorter than parameres; ventral plate of the median lobe almost parallel-sided in apical half, apex rounded, gonopore situated at apex of ventral plate (Figs. 30c, 31c), reaching ca. 0.8 of median lobe.
Redescription. Total length 6.9–8.0 mm; maximum width 4.5–4.8 mm; body oval, moderately convex.
Coloration. Dorsal black, with lateral margin of elytron reddish brown (Fig. 9). Maxillary palps and antenna yellowish brown. Ventral black to reddish brown, legs reddish brown.
Head. Clypeus weakly convex, surface with dense and fine punctures, anterior portion with denser punctures. Interstices between punctures smooth. Anterior margin of clypeus without marginal rim. Frons with punctures sparser than those on clypeus. Eyes of moderate size, separated by ca. 5× as wide as one eye, distinctly emarginate anteriorly in lateral view, smooth medially. Maxilla with glabrous basistipes. Mentum transverse, glabrous, strongly impressed anteromedially, lateral sides with series of fine setae. Submentum reddish brown, pubescent. Labial palps rather stout, palpomere 1 minute, palpomere 2 strongly widened distally, with dense brush of long yellow setae on its inner face and distal margin, palpomere 3 longest. Antennal scapus longest, rather thick, ca. 7.5× as long as pedicellus, antennomere 3 thin and a little shorter than pedicellus, antennomeres 4 and 5 almost equal in length, slightly widening distally, club densely pubescent, with few long setae, compact, ca. 2.5× as long as wide.
Prothorax. Pronotum moderately convex, widest basally, arcuately narrowed in front, with punctures sparser than those on vertex, interstices between punctures smooth; posterior margin slightly arcuate. Prosternum strongly tectiform, with median carina and a distinct tooth anteromedially.
Meso- and metathorax. Scutellum distinctly longer than wide, apex rounded, in shape of isosceles triangle, with punctation similar to those on pronotum. Elytron moderately convex, sutural stria deeply impressed in posterior half; each elytron with 10 longitudinal serial punctures, deeply impressed in posterior half, intervals with fine ground punctures, each puncture attached with two short transverse microsculpture especially in posterior half (Fig. 54), series 3+4 and 6+7 linked together subposteriorly, others serial punctures reaching end of elytron, the outer 4 serial punctures larger and deeper than the inner 6 serial punctures. Anteromedial portion of metaventral process with a strongly depressed pit (Fig. 58).
Legs. Reddish brown, rather short. Procoxae globular, pubescent; profemora without pubescence ventrally; protarsomeres unpubescent ventrally. Ventral surface of meso- and metafemora without pubescence, with sparse punctures and microsculptures; meso- and metatarsomeres with sparse pubescence ventrally, almost equal in length.
Abdomen. Pubescent, ventrite 1 with complete median carina, other ventrites uniformly convex. Posteromedial portion of ventrite 5 unpubescent, with fine punctures, posterior margin of ventrite 5 rounded, with fine marginal bead, without stria (Fig. 62).
Male genitalia (Figs. 30–38). Aedeagus around 1.2 mm long, ca. 2.7× as long as wide. Phallobase shorter than parameres, with short manubrium and rounded posteriorly. Parameres widest basally, gradually narrowing toward apex, outer margin straight, slightly sinuate, slightly or strongly curved inwards apically. Median lobe ca. 0.8–0.9× as long as parameres, widest in the basal 0.25 or at midlength, outer margin nearly parallel-side or slightly narrowing towards apex, rounded anteriorly, dully pointed apically; ventral plate of median lobe widest basally, almost parallelsided in apical half, apex rounded, gonopore situated at apex of ventral plate (Figs 30c, 31c), reaching ca. 0.8 of median lobe.
Biology. Unknown. The species was considered as aquatic in the original description (Sharp 1873), based on the information from the collector (G. Lewis) that it is ‘common in ponds’. Satô (1960) questioned the habitat of D. latum and suspected the species to be a synonym of D. hydrophiloides. We suspect that the habitat information in the original description was likely based on the confusion with some Coelostoma species which are common in Nagasaki, of the similar morphology, coloration and body size as D. latum, and are aquatic. All species of Dactylosternum known so far are terrestrial species (Hansen 1991; Fikáček 2010), including the other species treated here (D. frater, D. pseudolatum and D. salvarzai) which are very similar and likely rather closely related to D. latum. We hence assume that D. latum is a terrestrial species living in decaying plant material.
Remarks. This species was described based on two specimens collected by George Lewis in Japan. It had not been reported since the original description (Sharp 1873). Orchymont (1925) described D. vitalisi as a new species from Laos (type locality) and Fujian without examining the type specimens of D. latum. Dactylosternum vitalisi is also a large-sized species (more than 6 mm long) and is similar with D. latum. The examination of the holotype of D. vitalisi from Laos confirmed it represents the same species as the examined type specimens of D. latum. Surprisingly, the examined paratype of D. vitalisi is not identical to the holotype and is more similar to D. pseudolatum sp. nov., especially in the shape of aedeagus. This indicates the type series of D. vitalisi contains two species. We hence consider D. vitalisi is a junior synonym of D. latum.
Variability. This species is morphologically variable, especially in the shape of aedeagus, as illustrated in Figs. 33–38.
Distribution. China (Anhui, Fujian, Hunan, Guangxi, Yunnan); Japan (Nagasaki, based on historical specimens only). New for China. Outside of China and Japan, the species if known from: Laos (Orchymont 1925).
description: Published as part of Mai, Zuqi, Hu, Jian, Minoshima, Yûsuke N., Jia, Fenglong & Fikáček, Martin, 2022, Review of Dactylosternum Wollaston, 1854 from China and Japan (Coleoptera, Hydrophilidae, Sphaeridiinae), pp. 269-300 in Zootaxa 5091 (2) on pages 285-289, DOI: 10.11646/zootaxa.5091.2.3, http://zenodo.org/record/5843837