Taxonomic review of genus Microrhagus Dejean, 1833 from Korea, with description of a new species (Coleoptera, Eucnemidae, Melasinae, Dirhagini)

Abstract The genus Microrhagus Dejean, 1833 is reviewed with four species from Korea: Microrhagusfoveolatus (Fleutiaux, 1923), Microrhagusjejuensissp. n., Microrhagusmystagogus (Fleutiaux, 1923), and Microrhagusramosus (Fleutiaux, 1902). Herein, all Korean Microrhagus species are redescribed. A key to species of Korean Microrhagus and photographs of the diagnostic characters are also provided.


Introduction
The tribe Dirhagini Reitter, 1911 is a large group of the subfamily Melasinae with a worldwide distribution. Dirhagini is characterized by crenulate or incomplete pronotal lateral carina, most also with well-developed notosternal antennal grooves, an apical sex-comb on male protarsomere I, and without basal struts of the aedeagal median lobe (Muona 1993(Muona , 2011. The genus Microrhagus Dejean, 1833 is the largest genus in its tribe, with more than 130 species worldwide and 17 species in the Palaearctic Region, including seven species from Japan (Muona 2007(Muona , 2011Kovalev 2013Kovalev , 2016. Only Microrhagus ramosus was known from Korea (Suzuki 2014).
We review genus Microrhagus with four species, including an undescribed species, Microrhagus jejuensis sp. n., and two previously unreported species, Microrhagus foveolatus (Fleutiaux, 1923) and M. mystagogus (Fleutiaux, 1923) from Korea. A key to species of Korean Microrhagus, diagnoses, redescriptions, and photographs for the diagnostic characters are provided.

Materials and methods
Most samples examined were collected using flight intercept traps between 2015 and 2016. Samples were preserved in 95% ethanol and made into dried specimens by double mounted method (pinned with a micropin to a block of cork, which is mounted on a standard insect pin) for exact identification. To examine the antennae, legs, and aedeagus, specimens were softened in boiling water for 30-60 minutes and dissected using forceps and micro-pin probes. Dried specimens were examined under a microscope (S8APO, Leica, Germany) and separate organs were observed under a microscope (DM4000B, Leica, Germany). Photographs were taken using EOS-600D, CANON camera, through MP-E 65mm lens.
All specimens (including types) are deposited in the insect collection of the College for Agriculture and Life Sciences, Seoul National University (CALS, SNU, Seoul, Korea).
The concept of genus Microrhagus follows Muona (1993) and morphological terminology follows Muona (1993) and Otto (2016). Lateral lobes and secondary lateral lobes of aedeagus refer to the lateral and mesal apices of the parameres, respectively.
Identification of species was done using Fleutiaux (1902Fleutiaux ( , 1923Fleutiaux ( , 1935 and Hisamatsu (1960Hisamatsu ( , 1985. Identifications were rechecked by J. Muona who has examined the relevant type specimens of Palaearctic species of Microrhagus, including Microrhagus pectinicornis, closely similar to new species. Also, W. Suzuki confirmed identifications in process. Pronotum without groove at midline; elytra less than 2.5 × longer than combined width; male antennomere III with process at base, antennomere IV with process at mid-length, antennomeres V-X with processes at apex; lateral lobes of aedeagus narrowly produced apically . Dirhagus foveolatus Fleutiaux, 1923: 308. Diagnosis. Body: mostly shiny black. Head: frons with a weak carina at midline; antennae pectinate from antenomere III in male. Prothorax: pronotum with sparse punctures, average distance between punctures greater than puncture diameter, disc with paired dimples near middle; notosternal antennal grooves slightly widened posteriorly. Pterothorax: elytra 2.5 × longer than combined width; metepisternum gradually widened posteriorly, its greatest width narrower than outer edge of metacoxal plate; metacoxal plate expanded inward; abdominal ventrite V narrowly rounded at apex. Redescription. Male (Fig. 1A, C-D) 5.1-6.0 mm long and 1.6-1.9 mm wide. Body mostly black; tarsi yellow-brown; surface glossy, with yellow pubescence. Head with circular and regularly sized punctures, denser at frontoclypeal region; frons with a weak carina at midline; frontoclypeal region slightly depressed at base, broadly rounded, with anterior edge slightly sinuate, anterior edge 3.7 × wider than distance between antennal sockets (Fig. 1G). Antennae (Fig. 1E) almost reaching metacoxal plate, with yellow-brown pubescence, and pectinate from antennomere III; processes of antennomeres III, IV, and V 1.1, 2.1 and 2.1 × as long as corresponding antennomeres; antennomere I robust; antennomere II shortest; antennomere III with process near base, 1.7 × longer than II, and 1.3 × longer than IV; antennomere IV with process at mid-length; antennomeres V-X with processes near apex; apical antennomere strongly elongate, curved, 9.5 × longer than wide, and 2.5 × longer than previous one. Pronotum 1.2 × wider than long, subparallel-sided near base, gradually narrowed anteriorly; surface with punctures, average distance between punctures greater than puncture diameter; disc with paired dimples near middle and a short carina at base of midline; anterolateral carina exceeding half as long as pronotum; posterolateral carina almost reaching pronotal mid-length, fused with anterolateral carina in some; antescutellar area almost straight in dorsal view; pronotal posterior angles sharply projecting, exceeding posterior edge of antescutellar area. Scutellum slightly raised, 1.1 × longer than wide, gradually narrowed posteriorly, and rounded at apex; surface coarse, densely punctate, pubescent with dense setae, especially at apex. Elytra 2.5 × longer than combined width, gradually narrowing posteriorly; disc striate, with irregularly sized and spaced punctures; interstriae moderately convex, with several large, deep punctures near apices; apices simply rounded. Prosternum with curved sides, anterior margin shallowly bisinuate; punctures slightly denser anteriorly and posteriorly; prosternal process stout, tapered and curved dorsally at posterior end; hypomeron with punctures less than on prosternum; notosternal antennal grooves (Fig. 1I) slightly expanded posteriorly, sparsely punctate, glabrous, and with pits. Mesoventrite with irregularly sized punctures; mesopleuron with rough surface, especially anteriorly. Metaventrite with finer and denser punctures than on prosternum, especially at middle; disc with a weak median groove, not reaching anterior edge; metepisternum (  (Fleutiaux, 1923). widened posteriorly, its greatest width four-fifths of outer edge of metacoxal plate; metacoxal plate ( Fig. 1K) expanded inward, medially 2.3 × wider than laterally. Legs (Fig. 1O) slender; metatarsomere I 1.2 × longer than II-IV combined; metatarsomere II 1.3 × longer than III; metatarsomere V 1.7 × longer than II; claws simple. Abdomen with finer punctures than metaventrite; ventrite V narrowly rounded at apex (Fig. 1L). Aedeagus ( Fig. 1M-N) 4.3 × longer than wide; median lobe slightly curved ventrally, bifurcate at apex; lateral lobes as long as median lobe, feebly curved ventrally, blunt at apex, and with basally attached secondary lateral lobes; secondary lateral lobes shorter than lateral lobes, bent ventrally, parallel-sided, blunt at apex, and with long setae; ventral lobe as long as median lobe, gradually expanded apically, broadly truncate at apex, and densely pubescent; phallobase rectangular, 1.8 × longer than wide, one-third as long as entire aedeagus. Female (Fig. 1B) is distinguished from male by follow-ing characters: body stouter, 5.3-6.4 mm long and 1.7-2.1 mm wide; frontoclypeal region with anterior edge, 3.5 × wider than distance between antennal sockets (Fig. 1H); antennae ( Fig. 1F) serrate, not reaching metacoxal plate; antennomere II short, as long as IV; antennomere III 1.9 × longer than wide, 1.7 × longer than each length of II and IV; antennomeres IV-X gradually increasing in length, narrowing, and more strongly toothed toward antennal apex; apical antennomere 3.5 × longer than wide, 2.2 × longer than X.
Description. Holotype male ( Fig. 2A, C, D) 5.2 mm long and 1.5 mm wide. Body mostly black; antennomere II, antennal processes, mandible, and tibiae red- brown; maxillary palpi and tarsi yellow-brown; surface glossy, with yellow pubescence. Head with circular, irregularly sized punctures, especially at frontoclypeal region; frons with a short median groove; frontoclypeal region slightly depressed at base, broadly bifurcate and feebly concave at anterior edge, anterior edge 3.9 × wider than distance between antennal sockets (Fig. 2G). Antennae (Fig. 2E) almost exceeding abdominal ventrite I, with yellow-brown setae, and pectinate from antennomere III; processes of antennemeres III, IV, and V 1.1, 1.7, and 1.8 × as long as corresponding antennomeres; antennomere I robust; antennomere II shortest; antennomere III 1.7 × longer than II, as long as IV; antennomeres III-X with processes near apex, gradually lengthened apically; apical antennomere elongate, curved, 7.3 × longer than wide, and 1.9 × longer than previous one. Pronotum 1.3 × wider than long, subparallel-sided near base, gradually narrowed anteriorly from basal two-thirds; surface mostly with finer, sparser, and more regularly sized and spaced punctures than on head, larger and denser at sides; disc with a paired dimples near middle and a groove at midline, weakly swollen posteriorly; anterolateral carina short, almost one-third as long as pronotum; posterolateral carina almost reaching three-fifths length of pronotum; antescutellar area almost straight, weakly sinuate in dorsal view; pronotal posterior angles sharply projecting, slightly extended outward, and exceeding posterior edge of antescutellar area. Scutellum slightly raised; 1.2 × longer than wide, gradually narrowed posteriorly, and rounded at apex; surface coarse, densely pubescent. Elytra 2.7 × longer than combined width, parallelsided, gradually narrowing near apices; disc striate, with irregularly sized and spaced punctures; interstriae weakly convex, with several large and deep punctures near apices; apices simply rounded. Prosternum with curved sides, slightly widened anteriorly, and anterior margin shallowly bisinuate; surface mostly with larger, sparser, and more regularly sized and spaced punctures than on head, especially at center; prosternal process robust, gradually tapered and curved dorsally at posterior end; hypomeron with rough surface, with larger, denser punctures than on prosternum; surface rugose at coxal cavities; notosternal antennal grooves (Fig. 2I) slightly widened posteriorly, with outer marginal carina, with several irregularly sized and spaced punctures posteriorly, glossy, and with pits. Mesoventrite with coarse surface, with shallow punctures; mesopleuron with rough surface, especially anteriorly. Metaventrite mostly with finer and denser punctures than on prosternum; disc with a groove at midline, not reaching anterior edge; metepisternum (Fig. 2J) narrow, gradually widened posteriorly, its greatest width as wide as outer edge of metacoxal plate; metacoxal plate ( Fig. 2K) expanded inward, medially 1.6 × wider than laterally. Legs (Fig. 2O) slender; metatarsomere I 1.5 × longer than II-IV combined; metatarsomere II 1.3 × longer than III; metatarsomere V 1.2 × longer than II; claws simple. Abdomen with finer and denser punctures than on metaventrite; ventrite V narrowly rounded at posterior edge (Fig. 2L). Aedeagus (Fig. 2M-N) 4.3 × longer than wide; median lobe curved ventrally near apex, broadly bifurcate at apex with setae; lateral lobes slender with apical tooth inward, truncate and with long setae at apex; ventral lobe shorter and broader than median lobe, almost truncate at apical edge; phallobase globose basally with concave sides near apex, 1.5 × longer than wide, one-third as long as entire aedeagus. Allotype female (Fig. 2B) like male, except for following characters: 6.1 mm long and 1.8 mm wide; frontoclypeal region with anterior edge, 3.7 × wider than distance between antennal sockets (Fig. 2H); antennae (Fig. 2F) serrate, not exceeding metacoxal plate; antennomere III subrectangular, approximately twice longer than wide, 1.7 × longer than II, and 1.3 × longer than IV; apical antennomere 5.3 × longer than wide, and 1.8 × longer than X.