Dactylosternum nanlingensis Mai et Jia, 2022

Mai, Zuqi, Hu, Jian, Minoshima, Yûsuke N., Jia, Fenglong & Fikáček, Martin, 2022, Review of Dactylosternum Wollaston, 1854 from China and Japan (Coleoptera, Hydrophilidae, Sphaeridiinae), Zootaxa 5091 (2), pp. 269-300 : 278-281

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Dactylosternum nanlingensis Mai et Jia

sp. nov.

Dactylosternum nanlingensis Mai et Jia , sp. nov.

( Figs. 3 View FIGURES 1–4 , 11–13 View FIGURES 11–16 , 17 View FIGURES 17-19 , 23 View FIGURES 20–24 , 39, 42, 45 View FIGURES 39–47 , 49 View FIGURES 48–63 , 64, 66 View FIGURES 64–69 ).

Type material examined. HOLOTYPE: male ( SYSU), Guangdong, Ruyuan County, Tianjingshan National Forest Park, 24°43′19″N 114°2′51″E, fallen rotten wood in forest, 589 m, 16.IV.2020, Zuqi Mai, Baoping Huang & Zhaoyang Tang leg. GoogleMaps PARATYPES: 1 male, 5 females ( SYSU): same information as the holotype ; 1 male, 1 female ( SYSU), Jiangxi, Ganzhou, Jiulianshan National Reserve, Xiasongtang , 24°32′28″N 114°27′32″E, under fallen rotten wood, 526 m, 18.VIII.2020, Zhenming Yang leg. GoogleMaps

Diagnosis. Length 4.2–4.5 mm, ca. 1.4× as long as wide, widest at midlength. Body broadly oval, outline not parallel ( Fig. 3 View FIGURES 1–4 ), strongly convex ( Figs. 12–13 View FIGURES 11–16 ). Antenna yellow-brown with club black, club loosely segmented ( Fig. 39 View FIGURES 39–47 ). Surface of vertex, pronotum and elytron with fine punctures and microsculpture, each puncture connected with two short diverging lines forming a flying-bird-like impression ( Fig. 45 View FIGURES 39–47 ). Elytra slightly explanate in posterior half, sutural stria reaching ca. one-thirds of elytra posteriorly, with 10 rows of serial punctures, all nearly reaching elytral base. Posterior margin of ventrite 5 with a broad marginal bead. Aedeagus ( Fig. 23 View FIGURES 20–24 ): Parameres pointed at apex. Median lobe a little shorter than parameres, outer margin nearly parallel-sided in the medial, gradually narrowing apical, gonopore situated at apex.

Description. Total length 4.2–4.5 mm (holotype: 4.3 mm); maximum width 2.7–2.8 mm (holotype: 2.75 mm); body broadly oval ( Fig. 3 View FIGURES 1–4 ), strongly convex ( Figs. 12–13 View FIGURES 11–16 ).

Coloration. Dorsal black, with lateral margin of elytron slightly paler ( Fig. 3 View FIGURES 1–4 ). Maxillary palps and antenna yellowish brown with club black. Ventral black, mouthparts and legs reddish brown, tarsomeres reddish yellow ( Fig. 11 View FIGURES 11–16 ).

Head. Clypeus weakly convex, surface with sparse, moderately coarse fine punctures, each puncture with a flying-bird-like microsculpture. Anterior margin of clypeus without marginal rim. Frontoclypeal suture weakly developed but distinct. Frons with punctures sparser than those on clypeus. Eyes of moderate size, nearly semicircular in dorsal view, separated by ca. 5.2× as wide as one eye, distinctly emarginate anteriorly in lateral view, smooth medially. Maxilla with basistipes bearing sparse long setae. Maxillary palps stout, palpomere 2 swollen, thicker than the following two palpomeres, palpomere 4 with obtuse apex, ca. 1.3× as long as penultimate. Mentum transverse, ca. 1.5× as wide as long, widest between anterolateral corners, slightly narrowing posteriorly, bearing sparse long setae, surface of mentum deeply concave anteromedially, lateral sides with series of fine setae. Submentum black, 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 longer than other ones, a little narrower and and about 2× as long as penultimate. Antennal scapus longest, rather thick, ca. 3.5× as long as pedicellus, antennomere 3 thin and a little shorter than pedicellus, ca. 2× as long as antennomere 4, antennomeres 4 and 5 almost equal in length, slightly widening distally, without any seta, club densely pubescent, with few long setae, loosely segmented, ca. 6× as long as wide, antennomeres 7 and 8 almost equal in length, antennomere 9 symmetrical, ca. 1.8× as long as penultimate.

Prothorax. Pronotum transverse, strongly convex, arcuately narrowing anteriorly, anterolateral angles obtusely rounded, posterolateral angles almost rectangular, anterior and lateral margins with narrow marginal bead, pronotum surface with punctures similar to those on vertex ( Fig. 45 View FIGURES 39–47 ). Posterior margin slightly arcuate. Prosternum weakly tectiform medially, without median carina.

Meso- and metathorax. Scutellum slightly wider than long, in shape of equilateral triangle, with fine punctures similar to those on pronotum. Elytron strongly convex, sutural stria reaching ca. one-third of elytra posteriorly, with 10 longitudinal serial punctures, all nearly reaching elytral base, series 1–6 consisting of very fine and sparse punctures, lateral four series with punctures larger and deeper than in inner six series, series 5+6 linked together subposteriorly. Elytral intervals with fine punctures similar with those on pronotum ( Fig. 49 View FIGURES 48–63 ). Elytral margin slightly explanate in posterior half. Hind wing ( Fig. 17 View FIGURES 17-19 ) well developed, with R-M loop widest at distal; RA 3+4 not attached to RA basally, forming a large opened radial cell; r3 absent; r4 present, connecting RA 3+4 to R-M loop; RA 3 short, well defined at apical portion; RA 4 fused with RP 1 forming a pigmented area, nearly reaching the margin of the wing apically, RP 1 attached to R-M loop basally; RP 2 forming a pigmented area wide on base, attached to R-M loop basally but not reaching the margin of the wing apically; RP 3+4 well developed, long and narrow, attached R-M loop basally, curved posteriorly and reaching wing margin apically; medial spur straight and sharp; MP 3+4 distinct, cambered, connected with MP 1+2, not attached to MP 3 apically; MP 3 and MP 4 +CuA 1 well defined, connected to basal portions of the veins proximally, reaching wing margin posteriorly; CuA 1 present, connect with MP 3 and MP 4 +CuA 1; CuA 2 well defined, reaching the posterior edge of the wing apically; AA 3 and AA 4 well defined, nearly reaching posterior margin of the wing; venation of anal field strongly reduced, composed of a short AP 3+4.

Legs. Reddish brown, rather short. Procoxae globular, pubescent; profemora bearing dense pubescence throughout; protarsomeres with dense pubescence ventrally.Ventral surface of mesofemora covered with pubescence on marginal portion ( Fig. 42 View FIGURES 39–47 ), metafemora without pubescence, with fine punctures and sparse microsculptures; meso- and metatarsomeres with dense pubescence ventrally, almost equal in length.

Abdomen. Pubescent, ventrite 1 with complete median carina. Posterior apex of ventrite 5 nearly truncate, with an incomplete marginal bead along margin.

Male genitalia ( Fig. 23 View FIGURES 20–24 ). Aedeagus about 0.9 mm long, ca. 2.6× as long as wide. Phallobase short, with manubrium short and rounded posteriorly. Parameres widest in the middle, gradually narrowing towards apex, outside slightly and smoothly curved. Median lobe a little shorter than parameres, wide throughout, ca. 3× as long as phallobase, gradually narrowing apical, gonopore situated apically.

Etymology. This species is named after the type locality, the Nanling Mountains.

Biology ( Figs 64, 66 View FIGURES 64–69 ). Specimens were collected from the surface of fallen wood in forest. The surface of the wood was wet and covered with thick layer of fulgal hyphae. Adults crawled quickly at the surface of the fallen wood.

Remarks. This species is quite similar to D. cycloides Knisch, 1921 from Indonesia and Malaysia and D. auripes Fauvel, 1883 ( Fig. 70 View FIGURES 70–71 ) from New Caledonia. These two species also have a loose antennal club and highly convex body. This new species can be distinguished from D. cycloides by posterior margin of ventrite 5 with a broad marginal bead (marginal bead not distinct in D. cycloides ), apex of median lobe rounded but sharper (with a duller apex in D. cycloides ). It differs from D. auripes by shallower and finer serial punctures on elytron (strongly impressed punctures in D. auripes ), inner 5 punctural series reaching elytral base (not reaching elytral base in D. auripes ), median lobe rounded apically (apex truncate in D. auripes ).

Distribution. China (Guangdong, Jiangxi).

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