Microserica viengvai Ahrens, Lukic

Ahrens, Dirk, Liu, Wangang, Lukic, Daniel & Bai, Ming, 2023, A taxonomic review of Microserica Brenske, 1894 from continental Asia (Coleoptera: Scarabaeidae: Melolonthinae: Sericini), Zootaxa 5241 (1), pp. 1-115 : 50-51

Microserica viengvai Ahrens, Lukic & Liu, new species

Fig. 18A–D

Type material examined. Holotype: Ô “Haut Mekong Vieng Vai 23.V.1918 R.V. de Salvaza / Brit Mus. 1921-89 / 1111 Sericini Asia spec.” ( BMNH) . Paratypes: 4 ÔÔ, 2 ♀♀ “Haut Mekong Vieng Vai 23.V.1918 R.V. de Salvaza ” ( BMNH, ZFMK), 7 ÔÔ, 4 ♀♀ “ Haut Mekong Vieng Vien 3.VI.1918 R.V. de Salvaza ” ( BMNH, ZFMK) .

Description of holotype. Length: 4.8 mm, length of elytra: 4.4 mm, width: 3.2 mm. Body oval, dark brown, head and pronotum with some greenish shine, antenna yellow, dorsal and ventral surface dull but with iridescent shine; dorsal surface glabrous.

Labroclypeus trapezoidal,distinctly wider than long,widest at base, lateral margins weakly convex and convergent to strongly rounded anterior angles; anterior margin weakly emarginate medially, margins weakly reflexed; lateral margins and ocular canthus produce an indistinct blunt angle; surface shiny, weakly convex medially, coarsely and densely punctate, with a few short erect setae; frontoclypeal fine, weakly curved. Frons dull, with dense, fine punctures; with a few single setae beside eyes, otherwise glabrous. Smooth area in front of eyes flat, 1.5 times as wide as long. Ocular canthus wide and short (1/3 of ocular width), its external margin straight, impunctate, with a terminal seta. Eyes small, ratio of diameter/interocular width: 0.57. Antenna with ten antennomeres; club composed of four antennomeres, straight, 1.1 times as long as remaining antennomeres combined, all lamella of club equal in length. Mentum elevated and slightly flattened anteriorly.

Pronotum wide, widest at base, lateral margins moderately convex and convergent to sharp, distinctly produced anterior angles, posterior angles blunt. Anterior margin of pronotum weakly convex, with fine, complete marginal line; basal marginal line absent; surface finely and densely punctate, with minute setae in punctures, lateral anterior margin and lateral margin sparsely setose. Hypomeron weakly carinate, not produced ventrally, not grooved. Scutellum small and triangular, finely and densely punctate, smooth along midline.

Elytra oval, widest at middle, striae distinctly impressed, finely and densely punctate, intervals convex, with fine and dense punctures only concentrated along striae, along middle almost impunctate, with minute setae in punctures, odd intervals with a few single, short white, adpressed setae; epipleural edge fine, ending convex external apical angle of elytra, epipleura densely setose; apical border membraneous, with a fine fringe of short microtrichomes (visible at ca 100x magnification).

Ventral surface dull, finely and densely punctate, metasternum on disc with long erect setae, otherwise sparsely covered with fine, short, or very minute setae; metacoxa glabrous, with a few single setae laterally. Mesosternum between mesocoxae as wide as mesofemur. Ratio of length of metepisternum/metacoxa: 1/1.83. Abdominal sternites finely punctate, with a transverse row of coarse punctures, each bearing a large, robust seta. Pygidium weakly convex and dull, with fine, dense punctures, without smooth midline, with a few long setae along apical margin, otherwise glabrous.

Legs moderately wide and long; femora finely and sparsely punctate, with two longitudinal rows of longer setae. Metafemur shiny, anterior margin acute, without submarginal serrated line; anterior row of seta-bearing punctures reduced; ventral posterior margin distinctly widened in apical half and entirely smooth, dorsal posterior margin also smooth, with a few short setae basally. Metatibia short and wide, widest at middle but only weakly narrowed towards apex, ratio width/length: 1/3.1; dorsal margin carinate, with two groups of spines, basal group at anterior third, apical one at three quarters of metatibial length, in basal third with a few fine, single setae; lateral face longitudinally convex, finely and sparsely punctate on dorsal and basal portion, glabrous; ventral margin finely serrate, with four equidistant setae; medial face smooth and glabrous, apex interiorly near tarsal articulation bluntly truncate. Tarsomeres with fine, sparse setae ventrally, neither laterally nor dorsally carinate, dorsally smooth; metatarsomeres ventrally glabrous, with a strongly serrated ridge ventrally, but without parallel subventral smooth carina; first metatarsomere much shorter than following two tarsomeres combined, little longer than dorsal tibial spur. Protibia short, bidentate; anterior claws symmetrical, basal tooth of both claws bluntly truncate at apex.

Aedeagus: Fig. 18A–C Habitus: Fig. 18D .

Diagnosis. Microserica viengvai Ahrens, Lukic & Liu, new species has not similar species on continual Asian mainland; its external appearance is similar to Microserica martini Ahrens, 2001 from Sumatra, differs, however, by the uniform dark and smaller body as well as by the shape of aedeagus: the phallobase is more compact and curved (lateral view), the parameres are inserted more asymmetrically; the left paramere is shorter and simple, and the right one is strongly widened and dorsoventrally flattened.

Etymology. The species name is derived from the name of its type locality, Vieng Vai (noun in apposition).

Variation. Length: 4.8–5.5 mm, length of elytra: 3.6–4.4 mm, width: 3.2–3.3 mm. Female: eyes slightly smaller, ratio of diameter/interocular width: 0.55; pygidium flat, antennal club short, composed of three antennomeres, distinctly shorter than remaining antennomeres combined.

Figures

FIGURE 18. A–D: Microserica viengvai Ahrens, Lukic & Liu, new species (holotype), E–H: Mic. namnao Ahrens, Lukic & Liu, new species (holotype), I–L: Mic. chaiyaphum Ahrens, Lukic & Liu, new species (holotype). A, E, I: Aedeagus, left side lateral view; C, G, K: Aedeagus, right side lateral view; B, F, J: Parameres, dorsal view; D; H, L: Habitus (not to scale). Scale: 0.5 mm.