A review of the genera Gnathochorisis Förster and Symplecis Förster of South Korea, with notes on Korean orthocentrines (Hymenoptera, Ichneumonidae, Orthocentrinae)

Abstract Two genera of Korean Orthocentrinae, Gnathochorisis and Symplecis, are reviewed, and keys to species of these genera are provided here. Two new species, Gnathochorisis fuscipes Humala & Lee, sp. n. and Gnathochorisis koreensis Humala & Lee, sp. n. are described from South Korea. The current state of the taxonomy of Eastern Palaearctic orthocentrines is briefly discussed.


Introduction
Orthocentrinae is a moderately large, cosmopolitan subfamily of small-bodied ichneumon wasps consisting of approximately 500 described species (Yu et al. 2012). Most orthocentrines are koinobiont endoparasitoids of nematoceran Diptera (Sciaroidea), the larvae of which often develop in fungal fruiting bodies (Roman 1923, Askew and Shaw 1986, Humala 2003. Only Orthocentrinae sensu stricto (Townes 1971), or the thochorisis is known in Mexico (Dasch 1992, Humala et al. 2011. The genus was also reported from Australia (Gauld 1984), Ecuador, and Central America (Veijalainen et al. 2012). Five species of Gnathochorisis, including two newly described, are presently reported from South Korea here. This is the first record of the genus from this country. In the European part of Russia G. flavipes Förster was reared from the fungus gnat Neoempheria striata Meigen (Mycetophilidae: Mycomyinae) (Humala 2003), other published host records (Dasch 1992) seem to be doubtful.
Head. 1.1 times as wide as high; frons nearly polished with weak microsculpture; face polished with sparse and fine punctures, at the level of antennal fossae 0.5 times as wide as head (Fig. 2). Inner eye orbits slightly divergent ventrally. Clypeus weakly separated from face, approximately 1.9 times as wide as high, edge of clypeus convex; malar space 1.8 times as long as mandible basal width, with subocular sulcus; maxillary palp reaching beyond fore coxa. In dorsal view, head posteriorly deeply concave; occipital carina complete; temples short; ocular-ocellar line 1.3 times as long as maximum diameter of lateral ocellus, equal to postocellar line (Fig. 3). Antenna moderately long, with 21 flagellomeres, basal flagellomere 3.9 times and second flagellomere 3.0 times as long as wide.
Mesosoma. 1.4 times as long as high. Mesoscutum matt with short adpressed dense setae; notauli well developed, meeting in the centre of mesoscutum (Fig. 3); epicnemial carina complete; in profile, scutellum somewhat high, without lateral carinae. Propodeum polished with sparse setae; anterior transverse carina strongly raised; area superomedia transverse, costula present; rounded apophyses of propodeum resulting from crossing lateral longitudinal and posterior transverse carinae developed. Spiracle of moderate size. Most of metapleuron polished with small coriaceous area near base of hind coxa. Fore wing without areolet, with 2rs-m shorter than second abscissa of 1m-cu (Fig. 4); cu-a inclivous, slightly postfurcal. Hind wing with first abscissa of Cu1 inclivous, 2 times as long as cu-a, distal abscissa of Cu1 present. Hind leg stout, coxa and femur polished, tibia and tarsus coriaceous, hind femur inflated, 3.2 times as long as high (Fig. 5). Hind tibia 4.8 times as long as its maximum width, with spine-like setae; hind basitarsus 0.4 times as long as hind tibia.
Male. Unknown. Etymology. Named after the fuscous hind legs.   (Humala 2007), it differs by the wide and entirely fuscous face, strong, distinct notauli meeting in the centre of the mesoscutum, short metasomal tergites, infuscate hind coxae, and stouter antennae. Description. Female (holotype). Fore wing length 3.3 mm. Head. 1.2 times as wide as high; frons nearly polished with weak microsculpture; face polished, sparsely and finely punctate, at the level of antennal fossae 0.45 times as wide as head (Fig. 8); inner eye orbits subparallel. Clypeus weakly separated from face, approximately 1.8 times as wide as high, edge of clypeus convex; temples short; ocularocellar line 1.3 times as long as maximum diameter of lateral ocellus, postocellar line 0.8 times as long as maximum diameter of lateral ocellus (Fig. 9). Antenna moderately long, with 20 (21 in paratype) elongate flagellomeres; basal flagellomere 4.5 times and second flagellomere 3.6 times as high as wide.
Mesosoma. 1.45 times as long as high. Mesoscutum convex, matt with short adpressed dense setae; epomia present; notauli well developed, meeting in centre of mesoscutum ( Fig. 9); epicnemial carina complete; in profile scutellum somewhat high, with lateral carinae anteriorly. Most of mesopleuron and metapleuron polished. Propodeum polished with sparse setae; carinae complete and strong; area superomedia slightly transverse (Fig. 10); small propodeal apophyses present; spiracle small. Fore wing with areolet closed, small, short petiolate and slightly longer than high; 3rs-m shorter than 2rs-m (Fig. 11); cu-a inclivous, nearly interstitial. Hind wing with first abscissa of Cu1 inclivous, 2 times as long as cu-a, distal abscissa of Cu1 present but weakly pigmented. Hind leg stout, coxa and femur polished, tibia and tarsus coriaceous; femur inflated, 3.0 times as long as high (Fig. 12); tibia 4.8 times as long as maximum width subapically, with spine-like setae and dense fringe on apex well developed; hind basitarsus 0.35 times as long as hind tibia.
Male. Unknown. Etymology. Named after the type locality, Korea.
Distribution. Holarctic; in Palaearctic region it was reported from Europe, Siberia, Russian Far East (Humala 2003(Humala , 2007, Japan (Dasch 1992; no data on the examined material was provided), and South Korea (new record).

Genus Symplecis Förster, 1869
Symplecis Diagnosis. Inner eye orbits strongly convergent ventrally in female, slightly in male; clypeus small, weakly to more strongly separated from face by a groove; eye large; temple short; malar space very narrow with subocular sulcus; mandible small, usually not twisted; male antenna lacking tyloids. Notaulus short and deep; epicnemial carina complete; carinae of propodeum complete and strong. Fore wing with areolet present or absent, when present sessile or short petiolate, rectangular. First metasomal segment slender, with glymma lacking, its sternite fused to tergite. Second tergite coriaceous, or with longitudinal striae. Ovipositor usually short, almost straight, stout at base, slenderer in apical part, 0.4-0.9 times as long as hind tibia.
Remarks. Medium sized genus with 14 recognized species distributed worldwide: 11 species are known in the Palaearctic region, six in the Nearctic region (Dasch 1992), one in the Neotropical region, one in the Afrotropical region and one in the Oriental region (Yu et al. 2012).
Two species are reported from South Korea in this paper. This is the first record of the genus from this country. Both Korean species of Symplecis are Holarctic.

Discussion
The fauna of Orthocentrinae of the Eastern Palaearctic and Oriental regions has been extremely poorly studied. There are only six known species of orthocentrine in China and four species in Japan (Yu et al. 2012); nine more species, omitted by Yu et al. (2012), were recorded in Japan resulting from the treatment of Russian collections stored at the Zoological Institute RAS (Humala 2007). In the Catalogue of Ichneumonidae of Russian Far East (Kasparyan et al. 2012) there are 28 genera and 110 species of Orthocentrinae sensu Humala (including Microleptinae, Cylloceriinae and Diacritinae), though the fauna has been insufficiently studied in the region.
Korean orthocentrines are very poorly known. We have been conducting an inventory of this subfamily since 2014. Up to now only two species of Orthocentrinae from the genera Proclitus Förster, 1869 and Eusterinx Förster, 1869 were reported from South Korea (Choi et al. 2014). Besides these genera and two genera reviewed in this publication, during preliminary sorting of large orthocentrine collections stored at the Yeungnam University, thirteen more genera have been found to occur in South Korea, namely Orthocentrus, Picrostigeus Förster, Stenomacrus Förster, Batakomacrus Kolarov, Plectiscus Gravenhorst, Neurateles Ratzeburg, Apoclima Förster, Pantisarthrus Förster, Aperileptus Förster, Dialipsis Förster, Plectiscidea Viereck, Helictes Haliday, and Megastylus Schiødte. The consequent treatment of these materials is planned. All listed 17 genera found by us in South Korea are entirely or predominantly Holarctic and many of them are abundant and species-rich within temperate zones of the Palaearctic. Taking into account that the orthocentrine fauna of Japan and China is practically unstudied, the generic composition of the South Korean Orthocentrinae fauna could be compared with that of the Russian Far East, which contains approximately twice as many genera as Korea (eight Palaearctic genera: Aniseres Förster, Atabulus Rossem, Entypoma Förster, Fennomacrus Humala, Hemiphanes Förster, Proeliator Rossem, Catastenus Förster and Terminator Humala are not registered there). Most Korean species also occur in the Russian Far East (Humala 2007, Kasparyan et al. 2012). However some new species in the genera Megastylus, Eusterinx, Plectiscus and Orthocentrus have been discovered already, and they will be described in our forthcoming papers, devoted to the Korean fauna of the subfamily.