Taxonomic review of the genus Dirrhagofarsus in Korea (Coleoptera, Eucnemidae)

Abstract The genus Dirrhagofarsus is firstly recorded from Korea with three species: Dirrhagofarsuslewisi (Fleutiaux, 1900), Dirrhagofarsusmodestus (Fleutiaux, 1923), and Dirrhagofarsusunicolor (Hisamatsu, 1960). A key to Korean species of Dirrhagofarsus, with diagnoses, redescriptions, and photographs of important structures is provided. In this work, Dirrhagusmodestusf.unicolor Hisamatsu, 1960 is regarded as a valid species, Dirrhagofarsusunicolor (Hisamatsu, 1960), comb. n.


Introduction
The genus Dirrhagofarsus was originally characterized by strongly convex elytral apices, dilate tarsomere IV and shiny notosternal antennal grooves (Fleutiaux 1935). Ford and Spilman (1979) described the biology and larval features of the type species, Dirrhagofarsus lewisi (Fleutiaux) adding a new diagnostic feature, the lateral frontal carinae. Muona (1993) transferred two species to Dirrhagofarsus: Hypocaelus attenuatus Mäklin, 1845 and Dirrhagus modestus Fleutiaux, 1923. Subsequently, Otto et al. (2014 described Dirrhagofarsus ernae from North America. Also, Otto (2016) described Dirrhagofarsus foveicollis from Laos. Finally, Kovalev (2016) transferred Dirrhagus ferrugineus Reitter, 1889 to Dirrhagofarsus. Thus, genus Dirrhagofarsus included six species worldwide (Muona 2007;Otto et al. 2014;Otto 2016;Kovalev 2016). Hisamatsu (1960) described what he considered a light-coloured form of Dirrhagus modestus as Dirrhagus modestus f. unicolor. After that, Muona and Alaruikka (2007) commented that f. unicolor was proposed as infrasubspecific name and omitted it from their catalogue. However, JM studied four such specimens collected in Japan (Fukushima Pref., Fukushima City, Moniwa, 1976-06-19, male and two females;Fukushima Pref., Mt. Asahi, 1974-07-29;S. Ohmomo leg.) and observed that they were a distinct species. Although the holotype has not been studied, Hisamatsu (1960) provided excellent images of the characteristic aedeagus, and illustrations of all other features are also as he described. Close to that time, JS and SL discovered an apparently new Dirrhagofarsus species from Korea. After discussion, the authors concluded that the Korean and Japanese forms were identical. Species names given to infrasubspecific forms are usually unavailable; however, there are exceptions to this. If such names are proposed before 1 January 1961 (ICZN, article 10.2), they are available with the original authority unless the description includes information showing that the author intended it an infrasubspecific grouping. This is not the case with Hisamatsu (1960) and thus the name of this previously ignored species becomes Dirrhagofarsus unicolor (Hisamatsu, 1960), comb. n., stat. n.

Materials and methods
Most samples were collected using flight intercept traps, light trapping, or by hand during 2015 and 2016. Samples were preserved in 95% ethanol and made into dried specimens by the double mounted method (pinned with a micropin to a block of cork, which is mounted on a standard insect pin). In order to examine detailed structures, some specimens were softened in distilled water for an hour and dissected using a micro-pin and forceps. Photographs for each species were taken using a digital camera (Canon EOS-600D) through MP-E 65mm lens. Samples for this study are deposited in the insect collection of the College for Agriculture and Life Sciences, Seoul National University (CALS, SNU, Seoul, Korea).
Morphological terminology follows Muona (1993) and Otto (2016). We measured the length of the pronotum, from the anterior edge of the pronotum to the apex of pronotal posterior angle.
Redescription. Female (Fig. 1A-C) 6.1-7.7 mm long and 1.7-2.2 mm wide. Body brown to dark brown; antennae and legs red-brown; surface weakly glossy, covered with yellow-brown pubescence. Head deeply inserted into prothorax, barely visible in dorsal view; surface coarse, with circular, irregularly sized and spaced punctures, more rugose near occiput and frontoclypeal region; frons simple, without mediolongitudinal carina; frontoclypeal region ( Fig. 1E) slightly depressed at base, obtusely trilobate at anterior edge, anterior edge 2.7 × wider than distance between antennal sockets. Antennae (Fig. 1D) weakly serrate, almost reaching abdominal ventrite II, with yellow-grey pubescence; antennomere II conical and shortest; antennomere III 2.5 × longer than II, and 1.3 × longer than IV; antennomeres IV-X subequal, slightly shortened apically; antennomere XI 2.9 × longer than wide, and 1.5 × longer than X. Pronotum as long as wide and obtusely arcuate anteriorly; surface with finer, more regularly sized and regularly spaced punctures than on head, especially anteriorly; disc with a medio-longitudinal carina at basal half; anterolateral carina one-fifth as long as pronotum; posterolateral carina four-fifths as long as pronotum; antescutellar lobe obtusely notched; pronotal posterior angles acute, exceeding posterior edge of antescutellar lobe. Scutellum straight anteriorly and evenly arcuate behind anterolateral angles, 1.1 × wider than long; surface rough, sparsely pubescent. Elytra 2.65 × longer than combined width, parallel-sided in dorsal view, and attenuate near apices; disc weakly striate, with shallow, irregularly sized and spaced punctures; several large, deep punctures present near apices; apices strongly convex in lateral view, apices pointed and raised above ventrite V (Fig. 1F). Prosternum wider than long, slightly widened anteriorly; punctures finer and more regularly spaced than on head; prosternal process gradually tapered, and curved dorsally posteriorly; hypomeron with coarse surface, with larger punctures than on prosternum; antennal grooves ( Fig. 1H) well-developed, notosternal, parallel-sided, with lateral marginal carina, non-punctate. Mesoventrite with coarse surface. Metaventrite with punctures denser than on prosternum; with a weak median groove along length of metaventrite; metepisternum (Fig. 1I) slightly widened posteriorly, widest part 1.7 × wider than outer edge of metacoxal plate; metacoxal plate (Fig. 1J) medially four × longer than laterally. Legs (Fig. 1G) with metatarsomere II 1.6 × longer than III, as long as V. Abdomen with denser punctures than on metaventrite (Fig. 1K)  Distribution. Korea (New record), Japan, Nearctic Region (USA).

Remarks.
A female individual of Dirrhagofarsus lewisi is observed under bark of rotten fallen tree. Additionally, they were rarely collected at light traps. They were observed clicking as well as flying and running. Fig. 2 Dirrhagus modestus Fleutiaux, 1923: 308. Rhacopus modestus Hisamatsu, 1985. Dirrhagofarsus modestus Muona, 1993: 46. Diagnosis. Body: mostly coloured black. Head: frons with a weak medio-longitudinal carina; anterior edge of frontoclypeal region 2.9 × wider than distance between antennal sockets in male, 2.7 × wider in female; antennomere III 1.35 × longer than IV in male, 1.7 × longer in female. Pronotum: anterolateral carina one-sixth as long as pronotum; posterolateral carina four-fifths as long as pronotum. Pterothorax: elytra 2.7 × longer than combined width, apices with fairly convex apices in lateral view. Leg: metatarsomere II 1.6 × longer than III, as long as V. Aedeagus: 5.3 × longer than wide; lateral lobes as long as median lobe, phallobase trapezoidal, one-sixth as long as aedeagus.
Sexual dimorphism. Female (Fig. 3B) can be distinguished from male by following characters: body slightly stouter, 4.5-5.7 mm long and 1.3-1.7 mm wide; base of frontoclypeal region slightly wider, anterior edge 2.8 × wider than distance between