Metabacetus Bates, 1892

Fedorenko, D. N., 2021, Notes on the genera Aristopus, Cosmodiscus and Metabacetus (Coleoptera: Carabidae: Pterostichini: Abacetina), with description of three new species from Vietnam, Russian Entomological Journal 30 (4), pp. 413-429 : 414-416

Metabacetus Bates, 1892

Bates, 1892: 364; Straneo, 1938a: 151; Will, Park, 2008: 191.

Type species: Metabacetus immarginatus Bates, 1892 (by monotypy).

DIAGNOSIS. Macropterous species of small size (BL 5– 8.5 mm), uniform black, with antennal pedicel centrically inserted in scape, antennomeres 4–11 pubescent, pedicel glabrous but ventral seta, mentum pits well-developed, body integuments impilose, metatibia externally glabrous, pronotum impunctate, elytral interval 3 without discal setigerous pores, except for vestigial setigerous pore d2 (median) that lacks seta.

REDESCRIPTION. With characters of other Abacetina : frontal impressions sulciform, divergent towards anterior supra-ocular seta; pronotum with one, sulciform, basal fovea on each side; elytral parascutellar striole ‘missing’ (i.e., directly extended into stria 1 that lost its primary angular base); mesoventrite with medial groove to receive subcarinate posterior inclination of prosternal process; abdominal sternites not basally sulcate; metacoxa bisetose (inner seta missing), metatrochanter with seta; supra-ocular groove often directly extended into orbital groove (that between gena and neck).

Body ( Figs 1–3 ) convex, uniform black, dorsum mostly iridescent and slightly sericeous due to dense and very transverse microsculpture, body appendages and extreme lateral margins of both pronotum and elytra red. Body setation nearly complete.

Head rather small, without neck constriction; eyes large, almost hemispherical, nearly reaching maxillary grooves be-

3

neath; genae fairly long, smooth, subtransverse, meeting neck at sharp obtuse angle, anteroventrally without antennal grooves; frontal sulci reaching level of anterior supra-ocular seta, posteriorly diverging or slightly S-shaped at the seta. Labrum mostly subsinuate at apical margin. Mandibles rather long, narrow and slightly incurved apically, with ventral scrobal ridge straight or subconvex. Apical maxillary and labial palpomere fusiform. Mentum tooth triangular, narrowly rounded, faintly longitudinally grooved. Setation: two supraocular setae and one clypeal seta on each side; labrum sexsetose; submentum quadrisetose, mentum bisetose.

Pronotum quadrisetose, subquadrate. Sides rounded, finely beaded, subsinuate or straight in front of obtuse yet sharp basal angles, these with minute, almost imperceptible, blunt tooth; lateral margin distinctly explanate and reflexed or not. Base laterally oblique, without bead; apical bead obliterate in middle 1/5–1/3; basal transverse impression missing, apical one vague. Basal sulci narrow, deep, smooth to crenulate at bottom, slightly converging apicad, reaching base, and running on basal third.

Elytra parallel-sided, truncate basally, with distinct humeri, a nearly imperceptible humeral tooth and a slight preapical sinuation. Basal ridge entire, humeral angle obtuse or very so. Striae entire, deep, more or less distinctly punctate, stria 7 separately reaching apex, stria 8 adjoining humerus or lateral margin just outside. Intervals 8 and 9 subequally wide except basally, interval 9 with umbilical seta series (USS) consisting of 6–1–7 umbilical setae/setigerous pores ( US), i.e., six US in anterior group, seven (3+2+2) in posterior group, and one intermediate seta. Parascutellar seta at base of stria 2. Stria 7 with two setae before apex, apical one being smaller than preapical.

Ventral side: prosternum with median groove distinct or not, prosternal process not bordered. Metepisternum longer than wide. Metaventrite laterally and abdominal sternite II rather

Figs 4–18. Aedeagus of Metabacetus spp. : 4–5, 11, 15–16 — M. hermanni ; 6–7, 12, 17–18 — M. laotinus ; 8–14 — M. perakianus ; 4–12 — median lobe; 13, 15, 17 — right paramere; 14, 16, 18 — left paramere; 4, 6, 8, 13, 15, 17 — left aspect; 5, 7, 9, 14, 16, 18 — right aspect; 10–12 — ventral aspect; vc — ventral longitudinal carina. Scale bar: 1 mm.

Рис. 4–18. Эдеагус Metabacetus spp. : 4–5, 11, 15–16 — M. hermanni ; 6–7, 12, 17–18 — M. laotinus ; 8–14 — M. perakianus ; 4–12 — среднЯЯ долЯ; 13, 15, 17 — праваЯ парамера; 14, 16, 18 — леваЯ парамера; 4, 6, 8, 13, 15, 17 — слева; 5, 7, 9, 14, 16, 18 — справа; 10–12 — вентрально; vc — продольный вентральный киль. Масштаб: 1 мм.

densely punctate; mesepisterna basally, metepisterna, and sides of abdominal sternites III–V less distinctly so. Sternites IV–VI with one pair of obligatory paramedian setae. Sternite VII bisetose in male, quadrisetose in female, all setae marginal.

Legs slender, protibia not apically dilated, with two close lateroapical setae (spinules), apical seta being stronger than preapical. Setation otherwise as follows: Profemur without anterior (anteroventral) setae, with three posterior setae, basal, medioventral, and apical. Mesotibia with lateral armature consisting of moderately strong spiniform setae, 3–4 anterolateral and one posterolateral near distal anterolateral seta (not counting apical setae); inner setal brush (at posteromesal margin) continuous and nearly unspecialized, consisting of ca. 16 setae. Metatibia externally glabrous. Meso- and metatarsi with tarsomere 1 externally (anteriorly) sulcate and slightly shorter than tarsomeres 2 to 4 combined, without distinct lateral setae. Tarsomere 5 ventrally glabrous, dorsal (dorsolateral) seta almost median in position; tarsomeres 1 and 2 with dorsoapical setae (DAS), these being much shorter in metatarsi; pro- and mesotarsomere 4 with lamellate ventroapical setae. Basal three protarsomeres dilated and biserially squamose in male, basal two protarsomeres toothed at latero-apical angles in female.

Aedeagus (Figs 4–18): median lobe geniculate, with a well-developed longitudinal median carina in ventral curve; apex short, narrow, more or less triangular; internal sac unarmed. Parameres subequal in length, right one apically rounded and spoon-shaped.

Tergite VIII and sternite VIII in female as in Figs 26–26. Female genitalia (urite IX) and reproductive tract (examined in M. hermanni ): laterotergite ventrally with a long process which is directed apicad and bears a brush of longer setae at apex (Fig. 34); gonosubcoxite at apex with 2–3 very short, dense, apically blunt, setae; gonocoxite slender, crescent, as long as gonosubcoxite, with a small ensiform, apically blunt, ventral (outer) seta a third from base and double preapical nematiform seta, no dorsal setae; bursa copulatrix membranous, spermatheca convoluted and very long, consisting of ca. 60 tight turns.

GEOGRAPHIC DISTRIBUTION. Throughout the Oriental region.

HABITATS AND HABITS. Many adults of the three species reviewed below were collected at light at night, at the edges of broad-leaved monsoon forests at 600– 1.450 m altitudes. Those of the most common species M. hermanni occur in montane regions of Vietnam at 400– 1.700 m altitudes where they dwell in forest leaf-litter .

COMMENTS. Will and Park [2008] stated that most characters of Metabacetus are symplesiotypic while they described well-developed mentum pits, apparently apotypic character, for at least M. hermanni Will, 2008 . The fact that these pits have been reported [ Guéourguiev, 2013] for M. willi Guéourguiev, 2013 , and found in M. laotinus Straneo, 1938 and M. perakianus Straneo, 1938 , suggests monophyletic origin of the genus.

Another apotypic feature of Metabacetus , the elytra without discal setae, should be corrected because vestigial d2 has been found in all of the three species examined by me. It is very minute and thence hard to detect in M. hermanni , but more or less well traceable in M. laotinus and M. perakianus .

Figures

Figs 1–3. Dorsal habitus of Metabacetus spp.: 1 — M. hermanni, ♂ from Xuan Son NP; 2 — M. laotinus, ♀ from Cao Bang Province; 3 — M. perakianus, ♀ from Song Thanh NP. Рис. 1–3. Габитус дорЗально Metabacetus spp.: 1 — M. hermanni, ♂ иЗ Национального парка Суансон; 2 — M. laotinus, ♀ иЗ провинции Каобанг; 3 — M. perakianus, ♀ иЗ Национального парка Сонгтхань.