Gastroserica (Helioserica) horii Ahrens & Pham, 2023

Ahrens, Dirk & Pham, Phu, 2023, Updates on the taxonomy and distribution of Gastroserica Brenske, 1897, Microserica Brenske, 1894, and Moronoserica Ahrens, Lukic & Liu, 2023 (Coleoptera: Scarabaeidae: Sericinae: Sericini), Zootaxa 5346 (5), pp. 551-566 : 553-555

Gastroserica (Helioserica) horii Ahrens & Pham , new species

Figs. 1E–I

Type material examined. Holotype ♂ “ Vietnam, Cuc Phuong , 100km SE of Hanoi, V-1993, leg. Michio Hori / 1215 Sericini Asia spec.” ( ZFMK).

Description of holotype. Length: 5.2 mm, length of elytra: 3.8 mm, width: 3.4 mm. Body oval, body, antenna club, middle and hind legs, head, elytra, scutellum, and abdomen blackish dark, pronotum including anterior legs reddish brown, dorsal surface dull, nearly glabrous.

Labroclypeus elliptical, wider than long, widest at middle, lateral margins strongly convex and convergent to strongly rounded anterior angles; anterior margin weakly emarginate medially, margins weakly reflexed; lateral margins and ocular canthus produce a blunt angle; surface weakly shiny, medially convexly elevated, finely and moderately densely punctate, with numerous long, fine, erect setae; frontoclypeal suture finely incised and curved medially. Frons dull, with sparse, coarse punctures, beside eyes and behind frontoclypeal suture with a few single short setae, otherwise with minute setae in punctures. Smooth area in front of eyes 1.2 times as wide as long. Ocular canthus sparsely finely punctate, narrow and moderately long (1/3 of ocular width), with a terminal seta. Eyes small, ratio of diameter/interocular width: 0.56. Antenna with ten antennomeres; club composed of four antennomeres, slightly reflexed at apex, 1.1 times as long as remaining antennomeres combined. Mentum elevated and slightly flattened anteriorly.

Pronotum wide, widest shortly before base, lateral margins evenly convex and convergent to blunt but distinctly produced anterior angles, posterior angles moderately rounded. Anterior margin of pronotum weakly convex, with fine and complete marginal line; basal marginal line absent; surface finely and densely punctate, with minute setae in punctures, anterior and lateral anterior margins sparsely setose. Hypomeron carinate, weakly produced ventrally. Scutellum triangular, finely and densely punctate, on midline narrowly impunctate.

Elytra short, widest at middle, striae distinctly impressed, finely and densely punctate, intervals convex, with fine and sparse punctures concentrated along striae, with very minute setae in punctures, otherwise glabrous; epipleural edge robust, ending at slightly rounded external apical angle of elytra, epipleura densely setose, apical border chitinous, without a fringe of short microtrichomes (visible at ca 100x magnification).

Ventral surface dull, finely and densely punctate, metasternum 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: 1/1.68. Abdominal sternites finely punctate, with a transverse row of coarse punctures, each bearing a robust seta. Pygidium weakly convex and dull, with mixed finer and larger punctures, without smooth midline, with numerous short setae and a few longer in the larger punctures.

Legs moderately wide; femora finely and sparsely punctate, with two longitudinal rows of longer setae. Metafemur moderately shiny, anterior margin acute, without submarginal serrated line; anterior row of seta-bearing punctures present; ventral posterior margin finely serrate at apex, only weakly widened in apical half, dorsal posterior margin serrate, with a few short setae basally. Metatibia moderately long and wide, widest at middle, ratio width/length: 1/2.9; dorsal margin sharply carinate, with two groups of spines, basal group at middle, apical one at three quarter of metatibial length, in basal third with a few robust single setae; lateral face longitudinally convex, finely and sparsely punctate, along midline smooth, with minute setae in punctures; ventral edge finely serrate, with three robust equidistant setae; medial face smooth, apex interiorly near tarsal articulation sharply truncate. Tarsomeres with fine, sparse setae ventrally, neither laterally nor dorsally carinate, dorsally smooth; metatarsomeres glabrous, with a strongly serrated ridge ventrally and a parallel subventral smooth carina immediately beside it; first metatarsomere as long as following two tarsomeres combined, and twice as long as dorsal tibial spur. Protibia short, bidentate; anterior claws symmetrical, basal tooth of both claws bluntly truncate at apex.

Aedeagus: Figs. 1E–H . Habitus: Fig. 1I . Female unknown.

Diagnosis. Gastroserica (H.) horii new species is in external appearance most similar to G. (H.) simaoensis Ahrens, Lukic & Liu, 2023 . The new species differs by the shorter basal lobe of the right, much shorter paramere and by the in apical half wider left paramere (dorsal view), which is more compact; the phallobase is in G. (H.) horii new species strongly asymmetrical. In shape of aedeagus the species appears to be close to G. (H.) fumaria Ahrens, Lukic & Liu, 2023 and G. (H.) phukradung Ahrens, Lukic & Liu, 2023 , but the parameres of the new species are shorter and more compact.

Etymology. The name of the new species is dedicated to its collector, Michio Hori (noun in singular genitive case).

Distribution. So far known only from the type locality (Cuc Phuong) in Vietnam.

Figures

FIGURE 1. A–D: Gastroserica (Helioserica) kachin Ahrens & Pham, new species (holotype); E–I: G. (H.) horii Ahrens & Pham, new species (holotype). J–M: G. (Gastroserica) muongphangensis Ahrens & Pham, new species (holotype). A, E, J: Aedeagus, left side lateral view; C, H, L: Aedeagus, right side lateral view; G: Aedeagus, dorsal view; B, F, K: Parameres, dorsal view; D, I, M: Habitus (not to scale). Scale: 0.5 mm.