A review of the genus Orthocentrus Gravenhorst (Hymenoptera, Ichneumonidae, Orthocentrinae) from South Korea

Twenty six species of the genus Orthocentrus Gravenhorst occurring in South Korea are reviewed. This is the first record of the genus from South Korea. Fifteen species, O. brachycerus sp. nov., O. caudalis sp. nov., O. consobrinus sp. nov., O. flavescens sp. nov., O. koreanus sp. nov., O. leei sp. nov., O. leucostomus sp. nov., O. orientalis sp. nov., O. pacificus sp. nov., O. parvus sp. nov., O. pulchellus sp. nov., O. setosus sp. nov., O. tenuiventris sp. nov., O. trichophthalmus sp. nov. and O. trichoptilus sp. nov., are described as new, and ten more species are recorded from South Korea for the first time. Orthocentrus consobrinus sp. nov. is also reported from Russia, O. caudalis sp. nov. from China, and O. winnertzii from Japan. A key to Orthocentrus species occurring in South Korea is provided. The status of O. stigmaticus Holmgren, 1858 as a valid species is resurrected (stat. rev.).

Orthocentrus is a large and worldwide genus comprising 95 extant described species (Yu et al. 2016), with the majority of species in the Palaearctic and Neotropical regions. The European fauna of Orthocentrus was revised by Aubert (1978), however his revision cannot be considered exhaustive, since it is based only on his own material from the Mediterranean area and Holmgren and Thomson collections. The Eastern Palaearctic fauna of the genus is poorly studied -only eleven species have been recognized there: among them, four species were reported from the Russian Far East, two species from China and one species from Japan, the remaining species were reported from Iran (Yu et al. 2016). The genus Orthocentrus was not recorded from South Korea hitherto.
The aim of this work is to review the Korean species of the genus Orthocentrus, describe new taxa and provide an identification key to species occurring there.

6
Ovipositor 2.6 times as long as hind basitarsus and as long as hind femur (Fig.  3A Second tergite 2.0-2.9 times as long as posteriorly wide (Fig. 16G). Metasoma long and slender, about 2.0 times as long as head and mesosoma together ( 14 Inner orbits yellowish up to level of lateral ocelli (Fig. 9C); face fuscous, malar space creamy (Fig. 9D)  Description. Female. Fore wing length 3.0-3.5 mm. Face at level of antennal sockets 1.4 times as wide as high; face smooth, polished, sparsely and slightly punctate; eyes not setose; dorsal ridge of face in between antennal sockets with a median blunt low prominence; face profile straight except dorsally very slightly impressed; inner eye orbits slightly divergent ventrally; edge of clypeus straight; antennal sockets not on a distinct high shelf; subocular sulcus distinct, sharp, slightly bent towards occiput; maxillary palp reaching fore coxa. In dorsal view, head posteriorly concave, temples short; lateral ocellus separated from eye by its maximum diameter; POL 1.8 times as long as diameter of lateral ocellus; ocellar-ocular grooves present. Minimum distance between antennal sockets about 0.4× diameter of socket; antenna very short, with 19 flagellomeres (n = 15) gradually shortening towards apex of antenna; basal flagellomere 1.5 times as long as wide and about 0.4× of length of scape; scape slightly convex on inner surface, slightly concave on outer surface. Mesosoma polished; mesoscutum anteriorly with distinct notauli; in profile, scutellum weakly convex, metapleuron slightly convex; propodeum with posterior  transverse carina complete, strong and raised between lateral longitudinal carinae, lateromedian longitudinal carinae complete, lateral longitudinal carinae distinct, propodeal spiracle small. Legs robust; coxae polished, femora with coriaceous microsculpture, tibiae and tarsi coriaceous-granulate; hind femur 3.0 times as long as high, hind tibia 4.0 times as long as apically wide, with spine-like setae.
Wings not particularly narrow; fore wing without areolet; vein Rs nearly straight; vein Rs+2r meeting pterostigma at basal 0.45; vein cu-a opposite Rs&M; nervellus intercepted in lower third.
First tergite slightly widening posteriorly, 1.2 times as long as apically wide; coriaceous, with two distinct lateromedian longitudinal carinae and indistinct longitudinal striae, with transverse impressions originating at about middle of tergite, sloping posteriorly, meeting centrally.
Second tergite 0.9 times as long as posteriorly wide; coriaceous and longitudinally striate, sometimes with lateromedian longitudinal carinae in anterior half, anterior corners impressed and transverse groove near posterior margin bending anteriorly near lateral margins, forming a somewhat uplifted area medially with longitudinal striae; thyridia rounded. Third tergite with coriaceous microsculpture anteriorly; remainder of metasoma unsculptured, polished. Ovipositor thin, slightly upcurved, without subapical dorsal notch; ovipositor sheath narrow, with sparse setae.
Blackish brown; face yellow, sometimes laterally infuscate; inner orbits broadly whitishyellow up to occiput; antenna orange; malar area yellow posterior to malar sulcus and up to level of lower third of eye; mouthparts, fore and mid coxae, all trochanters and trochantelli yellowish creamy, remainder of fore and mid legs yellow; hind legs orange, posterior margins of tergites 1-4 brown. Sometimes lower mesopleuron and scutellum reddish-brown.
Male. Flagellum with 21 flagellomeres; face and frontal orbits yellow. Otherwise as in female.
Biology. Hosts unknown. Etymology. Named from the Greek βραχύς (short) and κέρας (horn) after the short antenna.
Comparison. Compared with the other species that have lenticular head, flattened and smooth face, short temples, and eyes glabrous, the fore wing areolet is absent and the flagellum with fewer than 20 flagellomeres, unlike in O. koreanus and O. consobrinus. From the allied O. leei it differs in the yellow face and frontal orbits up to the level of the lateral ocelli; the POL 1.8 times as long as diameter of an ocellus. Description. Female. Fore wing length 3.0 mm. Face at level of antennal sockets as wide as high; head smooth and polished, face with punctures; eyes not setose; dorsal ridge of face in between antennal sockets without a median prominence; face in profile straight, except just before antennal sockets impressed; edge of clypeus straight, antennal sockets on a shelf; malar space with distinct subocular sulcus which is bent towards occiput; maxillary palp reaching to beyond fore coxa. In dorsal view, head posteriorly concave; temples short; lateral ocellus separated from eye by a distance 1.3 times longer than its maximum diameter; POL 1.3 times as long as diameter of lateral ocellus, lacking ocellar-ocular grooves. Minimum distance between antennal sockets about 0.7× diameter of socket; antenna comparatively short and thick, with 24 flagellomeres (25 in paratype) which gradually shortening apically; first flagellomere 1.5 times as long as wide and about 0.4 times as long as scape; scape nearly parallel-sided. Mesosoma smooth and polished except postero-ventral corner of pronotum with short striae, mesoscutum with indicated notauli; in profile, scutellum weakly convex, metapleuron somewhat convex; propodeum with coriaceous microsculpture and with complete posterior transverse carina, lateromedian longitudinal carinae indistinct basally, spiracle small.
Legs all slightly flattened, broad; coxae and femora polished, tibiae and tarsi coriaceous-granulate; hind femur 3.1 times as long as high, hind tibia 3.6 times as long as apically wide; tibiae dorsally with spine-like setae; spurs curved apically.
Wings not particularly narrow, fore wing with areolet closed but 3rs-m weak, areolet longer than high, vein 2rs-m shorter than 3rs-m, 2m-cu meeting areolet at apical 0.6, vein Rs nearly straight; nervellus intercepted slightly below middle.
First tergite 2.0 times as long as posteriorly wide, in dorsal view, slightly wider at spiracles; coriaceous, with weak lateromedian longitudinal carinae, with transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite 1.2 times as long as posteriorly wide; coriaceous, with shallow transverse impressions originating at about middle of tergite, sloping anteriorly and posteriorly, not meeting clearly centrally; anterior thyridia small, contrastingly coloured. Third tergite coriaceous; remaining tergites smooth and polished; fourth tergite with coriaceous microsculpture antero-medially. Ovipositor slightly upcurved, thin, as long as hind femur, without dorsal notch; ovipositor sheath narrow, pointed, with setae longer than ovipositor sheath width and curved backwards, sparser basally.
Blackish brown except mouthparts and malar space pale, antenna dull yellow ventrally, infuscate over entire dorsal side. Clypeus apically and dorsal ridge of upper face between antennae narrowly yellowish, frontal orbits with small yellowish marks close to antennal sockets; sternites creamy, fore and mid legs and hind trochanters and trochantellus yellowish. Hind coxae brown in basal 2/3, hind femur brownish, except for more light basal third. Tergites 3 and 4 with light brown apical margin.
Male. Unknown. Biology. Hosts unknown. Etymology. Named from the Latin cauda (tail) after the unusually long ovipositor as long as the hind femur.
Comparison. This is a distinctive species on account of the very long, thin, slightly upcurved ovipositor, which is as long as the hind femur ( Description. Female. Fore wing length 4.0 mm. Face at level of antennal sockets 1.4 times as wide as high; smooth, polished, slightly punctate; eyes not setose; dorsal ridge of face inbetween antennal sockets with a low median blunt prominence; face profile straight except dorsally very slightly im-pressed; inner orbits divergent ventrally; edge of clypeus straight, antennal sockets not on a distinct high shelf; subocular sulcus distinct, sharp, slightly bent towards occiput; maxillary palp reaching beyond fore coxa. In dorsal view, head posteriorly moderately concave, temples short but distinct, lateral ocellus separated from eye by its maximum diameter, POL 1.1 times as long as diameter of lateral ocellus; ocellar-ocular grooves present. Minimum distance between antennal sockets about 0.8× diameter of socket; antenna short, with 21 flagellomeres elongate, gradually shortening towards apex of antenna; first flagellomere 1.8 times as long as wide and about half of the scape length; scape slightly convex on inner surface, slightly concave on outer surface. Mesosoma smooth and polished; mesoscutum anteriorly with distinct notauli; in profile, scutellum weakly convex, metapleuron slightly convex; propodeum with posterior transverse carina complete, strong and raised between lateral longitudinal carinae, lateromedian longitudinal carinae complete, lateral longitudinal carinae distinct, spiracle small. Legs robust; coxae polished, femora with coriaceous microsculpture, tibiae and tarsi coriaceous-granulate; hind femur 2.7 times as long as high, hind tibia 4.0 times as long as apically wide; tibiae with spine-like setae.
Wings not particularly narrow; fore wing with small narrow areolet, vein Rs straight posteriorly, vein cu-a opposite Rs&M, oblique; nervellus straight, intercepted below.
First tergite slightly widening posteriorly, 1.5 times as long as apically wide; coriaceous, with two indistinct lateromedian longitudinal carinae and indistinct longitudinal striae, with transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally.
Blackish brown; face brown, yellowish along upper margin, inner orbits broadly light yellow from centre of face to level of front ocellus, antenna proximally and ventrally yellowish; malar area yellowish posterior to malar sulcus and up to level of ventral edge of eye; mouthparts, fore and mid coxae, all trochanters and trochantelli yellowish brown, remainder of fore and mid legs orange; hind legs slightly darker, apical margin of second tergite light brown.
Male. Unknown. Biology. Hosts unknown. Etymology. Named from the Latin consobrinus (relative), after the conspicuous similarity to O. koreanus.
Comparison. Compared with the other species that have a lenticular head, flattened and smooth face, short temples, and eyes glabrous, the fore wing areolet is present, unlike Description. Female. Fore wing length 3.1 mm. Face at level of antennal sockets 1.4 times as wide as high; face smooth, polished, sparsely punctate, eyes not setose, dorsal ridge of face in between antennal sockets with a median blunt low prominence; face profile straight except dorsally very slightly impressed, inner orbits slightly divergent ventrally; edge of clypeus straight, antennal sockets not on a distinct high shelf; subocular sulcus well developed, nearly straight; maxillary palp reaching beyond fore coxa. In dorsal view, head posteriorly slightly concave, temples very short, lateral ocellus separated from eye by a distance 1.4 times longer than its maximum diameter, POL 1.6 times as long as diameter of lateral ocellus; ocellar-ocular grooves present. Minimum distance between antennal sockets about 0.4× diameter of socket; antenna with 20 flagellomeres elongate, first flagellomere about 3.0 times as long as wide and about 0.9 times as long as scape; scape slightly convex on inner surface, slightly concave on outer surface. Mesosoma smooth and polished; mesoscutum anteriorly with distinct notauli; in profile, scutellum particularly high, metapleuron slightly convex; propodeum with posterior transverse carina complete, strong and raised between lateral longitudinal carinae, lateromedian longitudinal carinae complete, lateral longitudinal carinae distinct, spiracle small. Legs robust; coxae polished, femora with coriaceous microsculpture, tibiae and tarsi coriaceous-granulate; hind femur 2.9 times as long as high, hind tibia 3.5 times as long as apically wide; tibiae with spine-like setae.
Wings not particularly narrow; fore wing without areolet; vein Rs nearly straight, fore wing with vein Rs+2r meeting middle of pterostigma; vein cu-a nearly interstitial (opposite Rs&M); nervellus straight, intercepted below.
First tergite stout, widening posteriorly, 1.2 times as long as posteriorly wide; coriaceous, with two lateromedian longitudinal carinae and longitudinal striae, with transverse impressions originating at about middle of tergite, sloping posteriorly, meeting centrally.
Second tergite 0.8 times as long as posteriorly wide; coriaceous and longitudinally striate, with developed lateromedian longitudinal carinae, anterior corners impressed and transverse groove near posterior margin bending anteriorly near lateral margins, forming a somewhat uplifted striated area medially; small thyridia contrastingly coloured. Third tergite longitudinally striate with transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Remainder of metasoma unsculptured, polished. Ovipositor thin, comparatively short, weakly upcurved, without subapical dorsal notch; ovipositor sheath narrow, with sparse setae.
Etymology. Named from the Latin flavesco (turn yellow) after the yellowish general body colouration.
Comparison. This is a distinctive species on account of the metasomal tergites 2-3 with strong transverse-diagonal furrows separating contrastingly coloured creamy latero-posterior corners. From the closely allied O. castellanus it differs in the absence of the fore wing areolet and fewer antennal flagellomeres. Description. Female. Fore wing length 3.7 mm. Face at level of antennal sockets as wide as high; face smooth, polished, slightly punctate, frons finely pustulate with hairs, temples with fine matt-like coriaceous sculpture; eyes not setose, face slightly prominent, inner orbits slightly divergent ventrally; dorsal ridge of face in between antennal sockets without a median prominence; profile straight except dorsal third slightly impressed, edge of clypeus straight, antennal sockets on a shelf; subocular sulcus distinct, slightly bent towards occiput; labial palp short; maxillary palp reaching slightly beyond fore coxa. In dorsal view, head posteriorly slightly concave, temples short, lateral ocellus distant from eye by its maximum diameter; POL 1.4 times as long as diameter of lateral ocellus; ocellar-ocular groove somewhat developed. Minimum distance between antennal sockets about 2/3 diameter of socket; antenna with 26-27 elongate flagellomeres (n=18) which gradually shorten apically; basal flagellomere 2.0 times as long as wide and about half of scape length; scape slightly convex on inner surface, slightly concave on outer surface. Mesosoma smooth and polished; mesoscutum with distinct notauli anteriorly indicated; in profile, scutellum somewhat high, metapleuron slightly convex; propodeum with posterior transverse carina present between lateral longitudinal carinae and pleural carina, area superomedia narrowed posteriorly, spiracle medium-sized.
Wings not particularly narrow; fore wing with vein Rs+2r meeting centre of pterostigma; areolet closed, small, almost petiolate, 2m-cu meeting areolet at apical 0.7, vein Rs bent towards wing apex; vein cu-a inclivous and slightly distad of Rs&M; nervellus intercepted in lower third.
First metasomal tergite elongate, slightly widening apically, 2.1 times as long as posteriorly wide, coriaceous-rugose, with two nearly parallel, complete or posteriorly almost complete lateromedian longitudinal carinae; with deep transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite 1.3 times as long as posteriorly wide, coriaceous-rugose and somewhat strigose; with the central area convex, bounded by well-defined anterolateral oblique furrows connected with posterior transverse impressions originating at about middle of tergite and meeting centrally; thyridia small, oval, contrastingly coloured. Third ter-gite slightly coriaceous anteriorly, all remaining tergites smooth and polished. Ovipositor slightly upcurved, thin, without dorsal notch; ovipositor sheath narrow, pointed, with long scarce setae.
Brown to dark brown except face, frontal orbits, malar space, lower temple, hind corner of pronotum, tegula, wing bases, fore and mid legs, narrow apical bands on tergites 2 and 3; hind trochanter and trochantellus and base of hind tibia yellowish brown, mouthparts and sternites creamy. Sometimes face infuscate laterally. Hind coxa apically yellowish-brown.
Male. Unknown. Biology. Hosts unknown. Etymology. Named after the type locality, Korea.  Description. Female. Fore wing length 2.9 mm.
Face at level of antennal sockets 1.4 times as wide as high; face smooth, polished, slightly punctate, eyes not setose, dorsal ridge of face in between antennal sockets with a median blunt low prominence; face profile straight except dorsally very slightly impressed, inner orbits divergent ventrally; edge of clypeus straight, antennal sockets not on a distinct high shelf; subocular sulcus distinct, gently bent towards occiput; maxillary palp reaching to fore coxa. In dorsal view, head posteriorly concave, temples short but distinct, lateral ocellus separated from eye by its maximum diameter, POL 1.2-1.5 times as long as diameter of lateral ocellus; ocellar-ocular grooves present. Minimum distance between antennal sockets about 0.6× diameter of socket; antenna short, with 18-20 flagellomeres gradually shortening towards apex of antenna; first flagellomere 1.7 times as wide as high and about half of length of scape; scape slightly convex on inner surface, slightly concave on outer surface. Mesosoma smooth and polished; mesoscutum anteriorly with distinct notauli; in profile, scutellum weakly convex, metapleuron slightly convex; propodeum with posterior transverse carina complete, strong and raised between lateral longitudinal carinae; lateromedian longitudinal carinae complete, lateral longitudinal carinae distinct, spiracle small. Legs robust; coxae and femora polished, femora partly with coriaceous microsculpture, tibiae and tarsi coriaceous-granulate; hind femur 2.7 times as long as high, hind tibia 3.3 times as long as apically wide; tibiae with spine-like setae.
Wings not particularly narrow; fore wing without areolet; vein Rs nearly straight, fore wing with vein Rs+2r meeting pterostigma at basal 0.45; vein cu-a slightly distad of Rs&M; nervellus intercepted below.
First tergite slightly widening posteriorly, 1.5 times as long as posteriorly wide; coriaceous, with two lateromedian longitudinal carinae and longitudinal striae, with transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite 0.9 times as long as posteriorly wide; coriaceous and longitudinally striate, anterior corners impressed and transverse groove near posterior margin bent anteriorly near lateral margins, forming a somewhat uplifted area medially; thyridia rounded and contrastingly coloured. Third tergite with anterior thyridia and coriaceous microsculpture in anterior half. Remainder of metasoma unsculptured, polished; Ovipositor comparatively thin, slightly upcurved, with shallow subapical notch; sheath narrow, with setae directed backward.
Blackish brown; face brown, inner orbits with small yellowish marks close to antennal sockets; clypeus and upper face, antenna orange; malar area posterior to malar sulcus yellowish; mouthparts whitish-yellow, fore and mid legs yellow; hind legs dull orange, hind coxa dark brown in basal 3/4, hind femur somewhat infuscate centrally; posterior margin of tergite 2 and tergite 3 anteriorly and posteriorly yellowish-brown; sternites creamy.
Male. Unknown. Biology. Hosts unknown. Description. Female. Fore wing length 2.7 mm. Face at level of antennal sockets as wide as high; head smooth and polished, face granulate, eyes not setose, dorsal ridge of face in between antennal sockets without a median prominence; face profile straight except just before antennal sockets impressed, edge of clypeus straight, antennal sockets on a shelf; malar space with narrow, almost straight subocular sulcus; maxillary palp reaching to beyond fore coxa. In dorsal view, head posteriorly concave, temples short, lateral ocellus distant from eye by a distance 1.1 times longer than its maximum diameter, POL 1.1 times as long as diameter of lateral ocellus, lacking ocellar-ocular grooves. Minimum distance between antennal sockets about 0.4× diameter of socket; antenna comparatively short and thick, with 22 flagellomeres (n = 3) which gradually shorten apically; first flagellomere about 2.0 times as long as wide and about 0.6 times as long as scape; scape nearly parallel-sided.
Legs slightly flattened, broad; coxae and femora polished, tibiae and tarsi coriaceous-granulate; hind femur 3.1 times as long as high, hind tibia 3.6 times as long as apically wide; tibiae dorsally with spine-like setae; spurs curved apically.
First tergite 1.8 times as long as posteriorly wide, in dorsal view, slightly wider at spiracles; coriaceous, with lateromedian longitudinal carinae, with weak transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite 1.3 times as long as posteriorly wide; coriaceous with dense striae, polished posteriorly, transverse impressions originating at about middle of tergite, sloping anteriorly and posteriorly, not meeting clearly centrally; anterior thyridia rounded, contrastingly coloured. Remaining tergites smooth and polished; third tergite with coriaceous microsculpture antero-medially. Ovipositor straight, thin, comparatively long, without dorsal notch; ovipositor sheath narrow, pointed, with setae longer than sheath width and slightly curved backwards.
Blackish brown except mouthparts and malar space creamy, sternites creamy, fore and mid coxa and all trochanters and trochantelli largely yellow, antenna dull yellow ventrally, infuscate over entire dorsal side. Hind coxae fuscous in basal 2/3, hind femur brownish, except for basal third. Clypeus apically and sometimes dorsal ridge of upper face between antennae narrowly yellowish, frontal orbits yellow to vertex. One paratype from Cheongdo-gun has a lighter face and hind legs.
Male. Unknown. Biology. Hosts unknown. Etymology. Named from the Greek λευκο (white) and στομα (mouth) after the creamy mouthparts.
Comparison. Compared with the other species that have antennal sockets on a shelf, the face is granulate, the inner orbits yellowish up to the level of the lateral ocelli, antenna comparatively short and thick, with 22 flagellomeres, malar space and mouthparts creamy, notauli well developed.
Face at level of antennal sockets 1.1 times as wide as high; face smooth and densely punctate, eyes not setose, dorsal ridge of face in between antennal sockets without a median prominence; face profile straight, slightly impressed dorsally, edge of clypeus straight, antennal sockets on a shelf; inner orbits subparallel; subocular sulcus distinct, nearly straight; maxillary palp long, reaching beyond to fore coxa. In dorsal view, head posteriorly concave, temples short, lateral ocellus distant from eye by a distance 1.5 times longer than its maximum diameter, POL 1.6 times as long as diameter of lateral ocellus. Minimum distance between antennal sockets about 0.6 × of the socket diameter; antenna with 22-24 flagellomeres (n = 10) which gradually shorten towards apex; first flagellomere 2.3-2.5 times as long as wide and 0.6 times as long as scape; scape nearly parallel-sided.
Legs slightly flattened; coxae and femora polished, tibiae and tarsi coriaceous; hind femur 2.8 times as long as high, hind tibia 4.0 times as long as apically wide; tibiae with spine-like setae, spurs of hind tibia distinctly curved apically.
Metasoma slender and considerably compressed from tergite 3 to apex. First tergite elongate, slightly widening posteriorly, 2.1 times as long as posteriorly wide; coriaceous-strigose, lateromedian longitudinal carinae weak and indistinct, with shallow transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite parallel-sided, 1.8 times as long as posteriorly wide; coriaceous and finely strigose, with shallow transverse impressions originating at about middle of tergite, sloping posteriorly, polished apically; small thyridia oval. Third tergite elongate, nearly 2.0 times as long as posteriorly wide, coriaceous medio-basally, polished in posterior half. Remaining tergites unsculptured. Ovipositor thin, slightly upcurved, without dorsal notch, pointed apically; ovipositor sheath narrow, parallelsided, with dense setae longer than sheath width and curved backwards.

Biology. Hosts unknown.
Etymology. This species is named from the Latin orientalis (eastern) after its geographical distribution, as the Korean Peninsula is situated in the Far East.
Comparison. Compared with the other species that have antennae on a shelf, it has a granulate face and no distinct yellow marks along the inner orbits, the first flagellomere 2.3-2.5 times as long as wide, the areolet comparatively small, the first tergite 2.1 times as long as posteriorly wide, the second tergite 1.8 times as long as posteriorly wide. Additionally, the subocular sulcus is nearly straight, the POL 1.6 times as long as the diameter of a lateral ocellus, and the fore wing length is 2.4-2. Description. Female. Body length 2.8-3.0 mm, fore wing length 2.2-2.5 mm. Face at level of antennal sockets 1.1 times as wide as high; face densely punctate, eyes with short indistinct setae, inner orbits divergent ventrally, vertex somewhat prominent; dorsal ridge of face in between antennal sockets without a median prominence; face profile slightly convex, edge of clypeus convex, antennal sockets on a shelf; subocular sulcus distinct, strongly bent towards occiput; maxillary palp long, reaching beyond to fore coxa. In dorsal view, head posteriorly concave, occipital carina weak, widely interrupted dorsally; temples distinct, lateral ocellus distant from eye by a distance 1.7 times longer than its maximum diameter, POL 1.2 times as long as ocellar diameter of lateral ocellus. Minimum distance between antennal sockets about 0.4× of the diameter of socket; antenna with 24-25 flagellomeres (n=9) which do not gradually shorten towards apex; first flagellomere about 1.1 times as long as wide and about 1/3 of the scape length; scape nearly parallel-sided.
Legs slightly flattened; coxae and femora polished, tibiae and tarsi coriaceous; hind femur 2.8 times as long as high, hind tibia 3.5 times as long as apically wide; tibiae with spine-like setae.
Wings not particularly narrow, fore wing with areolet closed, clearly transverse, narrowly sessile, 2m-cu meeting areolet at apical 0.7, vein Rs gently bent towards wing apex; vein cu-a distad of Rs&M; nervellus angled below the middle.
First tergite of metasoma elongate, slightly widening posteriorly, 1.6 times as long as posteriorly wide; coriaceous, lateromedian longitudinal carinae weak and indistinct, with shallow transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite nearly parallel-sided, 1.2 times as long as posteriorly wide; coriaceous, with transverse furrows originating at about middle of tergite, sloping posteriorly, meeting centrally; anterior thyridia small, oval, contrastingly coloured; second thyridia vaguely defined, medial, same colour as surrounding cuticle. Third tergite nearly as long as posteriorly wide, coriaceous medio-anteriorly, polished in apical part, with second thyridia round. Remaining tergites unsculptured. Ovipositor not visible; sheaths narrow, with dense setae curved backwards.
Body largely setose except pronotum, mesopleuron and metapleuron; setae scattered on anterior tergites and posterior sides of coxae.
Etymology. This species name refers to its geographical distribution -relating to the Pacific Ocean and the region where Korea is situated.
Comparison. Similar to O. fulvipes Grav. in having an occipital carina, subocular sulcus strongly bent towards the occiput, all legs entirely red, but differs in its smaller size (fore wing 2.2-2.5 mm), the anterior tergites coriaceous without longitudinal striae; the first tergite 1.6 times as long as posteriorly wide, the second tergite 1.2 times as long as posteriorly wide.

Orthocentrus parvus Humala & Lee, sp. nov.
http://zoobank.org/233D2588-17AC-4C8B-A8EB-7CFBE0613CB0 Fig. 12 Description. Fore wing length 1.7 mm. Face at level of antennal sockets 1.2 times as wide as high; face punctate, eyes not setose, dorsal ridge of face inbetween antennal sockets without a median prominence; face in profile almost evenly round, slightly more so dorsally, edge of clypeus slightly impressed, antennal sockets on a shelf but shelf not particularly high; subocular sulcus distinct, bent towards occiput; maxillary palp reaching to fore coxa. In dorsal view, head posteriorly slightly concave, temples narrow, lateral ocellus separated from eye by a distance 1.2 times longer than its maximum diameter, POL 1.1 times as long as diameter of lateral ocel- lus, lacking ocellar-ocular groove. Occipital carina reduced. Minimum distance between antennal sockets slightly more than half diameter of socket; antenna with 23 short flagellomeres which do not gradually shorten towards apex; basal flagellomere subquadrate and about 1/3 of length of scape; scape almost parallel-sided, internal surface slightly convex.
Legs broad, coxae and femora polished, tibiae and tarsi coriaceous-granulate; hind femur 2.9 times as long as high, hind tibia 4.0 times as long as apically wide; tibiae with spine-like setae.
Wings not particularly narrow; fore wing with areolet closed but 3rs-m weak, areolet nearly as wide as high, 2m-cu meeting areolet at apical 0.7, vein Rs straight; nervellus not intercepted, straight.
First tergite stout, posteriorly slightly widening, 1.4 times as long as posteriorly wide; coriaceous, without lateromedian longitudinal carinae, with transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite 1.2 times as long as posteriorly wide; coriaceous, with faint transverse impressions originating at about middle of tergite, slightly sloping posteriorly, not meeting centrally; thyridia contrastingly coloured. Remaining tergites smooth and polished. Ovipositor straight; ovipositor sheath with dense and long, curved backwards-directed setae.
Male. Unknown. Biology. Hosts unknown. Etymology. Named from the Latin parvus (small, inconspicuous) after its small size.
Comparison. Compared with the other species that have antennae on a distinct shelf and face finely punctate, the size is smaller (fore wing 1.7 mm), eyes without short setae, the POL shorter, the temples narrower, occipital carina not developed, unlike in O. pacificus. Additionally, compared with other small species, O. parvus has narrow temples, the subocular sulcus is bent and the first flagellomere subquadrate Distribution. Palaearctic; *South Korea (GG, GW).

Orthocentrus pulchellus
Humala & Lee, sp. nov. http://zoobank.org/1AF75673-BF1E-450E-9E7E-A5D7602A0318 Fig. 13 Description. Female. Fore wing length 3.1 mm. Face at level of antennal sockets 1.4 times as wide as high; face smooth, polished, sparsely punctate, eyes not setose, dorsal ridge of face in between antennal sockets with a median blunt low prominence; face profile straight except dorsally very slightly impressed, inner orbits slightly divergent ventrally; edge of clypeus straight, antennal sockets not on a distinct high shelf; subocular sulcus narrow, nearly straight; maxillary palp reaching beyond fore coxa. In dorsal view, head posteriorly concave, temples very short, lateral ocellus separated from eye by a distance of 1.8 times longer than its maximum diameter, POL 1.5 times as long as diameter of lateral ocellus; ocellar-ocular grooves present. Minimum distance between antennal sockets about half of the diameter of socket; antenna moderately long, with 30-31 flagellomeres elongate (n = 4); flagellum considerably thinned apically; first flagellomere about 3.5 times as long as wide and about 0.8 times as long as scape; scape slightly convex on inner surface, slightly concave on outer surface. Mesosoma smooth and polished; mesoscutum anteriorly with distinct notauli; in profile, scutellum high, metapleuron slightly convex; propodeum with posterior transverse carina complete, strong and raised between lateral longitudinal carinae, lateromedian longitudinal carinae complete, lateral longitudinal carinae distinct, spiracle small. Legs robust; coxae polished, femora with coriaceous microsculpture, tibiae and tarsi coriaceous-granulate; hind femur 2.9 times as long as high, hind tibia 3.7 times as long as apically wide; tibiae with spine-like setae.
Wings not particularly narrow; fore wing without areolet, vein 2rs-m about 0.6 times as long as portion of 1m-cu between 2rs-m and 2m-cu; pterostigma comparatively wide, vein Rs bent upwards, fore wing with vein Rs+2r meeting apical 0.6 of pterostigma; vein cu-a strongly oblique, distad of Rs&M; nervellus intercepted below.
First tergite 1.8 times as long as posteriorly wide; coriaceous, with two lateromedian longitudinal carinae and longitudinal striae, with transverse impressions originating at about middle of tergite, sloping posteriorly, meeting centrally.
Brown; face, frons and vertex yellowish, inner orbits broadly creamy-yellow up to occiput, interocellar area fuscous; antenna yellowish-brown; malar area yellow posterior to subocular sulcus and up to level of half of eye; mouthparts, fore and mid legs, hind coxa, trochanters and tarsi and longitudinal bars along notauli yellow; propleuron, lower and upper pronotum, medial part of mesoscutum anteriorly, scutellum, mesopleuron in lower half, hind coxa and trochanters and tarsi reddish brown; posterior margin of tergite 1and anterior corners and posterior margin of tergite 2 yellowish-brown; sometimes hind femur except basal 0.2 and hind tibia except light basal ring brown.
Male. Unknown. Biology. Hosts unknown. Etymology. Named from the Latin pulchellus (nice, pretty) after its rich body colouration.
Comparison. This is a distinctive species on account of the entirely yellow face and frons (except for the interocellar area), the absence of the fore wing areolet and the presence of yellow bars along the notauli on the median part of the mesoscutum.  Face at level of antennal sockets 1.2 times as wide as high; face coarsely papillate, eyes densely setose, dorsal ridge of face in between antennal sockets without a median prominence; face in profile almost evenly round, edge of clypeus very slightly im-pressed, antennal sockets on a shelf; subocular sulcus weak and shallow, slightly bent towards occiput; maxillary palp reaching to beyond fore coxa. In dorsal view, head posteriorly slightly concave, temples narrow, lateral ocellus separated from eye by a distance of 2 times longer than its maximum diameter, POL 1.1 times as long as diameter of lateral ocellus, lacking ocellar-ocular grooves. Minimum distance between antennal sockets slightly less than half diameter of socket; antenna comparatively short, with 26 short flagellomeres which do not gradually shorten towards apex; first flagellomere 0.8 times as long as wide and about as long as 1/3 of scape; scape almost parallel-sided. Mesosoma smooth and polished except dorsal propodeum coriaceous with punctures; mesoscutum lacking notauli; in profile, scutellum weakly convex, metapleuron slightly convex; propodeum with posterior transverse carina strong, present between lateral longitudinal carinae, lateromedian longitudinal carinae complete, and lateral longitudinal carinae present as short stubs not reaching spiracles, spiracle small.

Orthocentrus setosus
Legs broad, hind coxa large; coxae and femora polished, tibiae and tarsi coriaceousgranulate; hind femur 2.6 times as long as high, hind tibia 3.3 times as long as apically wide; tibiae with spine-like setae.
First tergite stout, apically widening, 1.5 times as long as posteriorly wide; coriaceous, without lateromedian longitudinal carinae, with transverse impressions originating at about middle of tergite, sloping posteriorly, not meeting centrally. Second tergite 0.7 times as long as posteriorly wide; coriaceous to rugose, with transverse impressions originating at about middle of tergite, slightly sloping posteriorly, meeting centrally; small transverse thyridia contrastingly coloured. Third tergite coriaceous with transverse furrow, posteriorly polished; remaining tergites smooth and polished. Ovipositor short, straight, without dorsal notch; ovipositor sheath invisible.

Orthocentrus stigmaticus
Face at level of antennal sockets 1.1 times as wide as high; face smooth and densely punctate, eyes not setose, dorsal ridge of face in between antennal sockets without a median prominence; face profile straight, slightly impressed dorsally, edge of clypeus straight, antennal sockets on a shelf; subocular sulcus distinct, bent towards occiput; maxillary palp long, reaching beyond to fore coxa. In dorsal view, head posteriorly slightly concave, temples distinct, lateral ocellus distant from eye by its maximum diameter, POL as long as diameter of lateral ocellus. Minimum distance between antennal sockets about 0.6× of the diameter of socket; antenna with 31-36 flagellomeres (n=10) which gradually shortening towards apex; first flagellomere 2.3-2.5 times as long as wide and about 1/2 of the scape length; scape nearly parallel-sided.
Legs slightly flattened; coxae and femora polished, tibiae and tarsi coriaceous; hind femur 3.4 times as long as high, hind tibia 3.8 times as long as apically wide; tibiae with spine-like setae, spurs of hind tibia distinctly curved apically.
Wings somewhat narrow, cells thus comparatively long and narrow; fore wing with areolet closed, large, conspicuously transverse, 2m-cu meeting areolet at apical 0.7, vein Rs gently bent towards wing apex; vein cu-a clearly distad of Rs&M; nervellus angled in the middle.
Face at level of antennal sockets 0.9 times as wide as high; face fairly sparsely punctate, shining, eyes setose, dorsal ridge of face in between antennal sockets without a median prominence; face profile gently curved, edge of clypeus somewhat impressed, margin straight, antennal sockets not on a distinct high shelf; subocular sulcus gently curved; maxillary palp long, reaching back to fore coxae. In dorsal view, head posteriorly moderately concave, temples distinct, lateral ocellus distant from eye by its maximum diameter, POL 1.1 times as long as diameter of lateral ocellus, ocellar-ocular grooves absent. Minimum distance between antennal sockets about 0.4× diameter of socket; antenna long, slender, with 45 flagellomeres which gradually shorten towards apex of antenna; first flagellomere 2.1 times as long as wide and 0.6 times as scape length; scape slightly curved, in frontal view a little concave on lateral surface, convex on inner surface.
Legs stout, hind leg massive; hind femur 3.1 times as long as maximum depth, hind tibia 4.1 times as long as apical width; tibiae lacking spine-like setae.
First tergite somewhat elongate and apically slightly widening, 1.6 times as long as posteriorly wide; heavily rugose without lateromedian longitudinal carinae, with transverse impressions originating at about middle of tergite, sloping posteriorly, and meeting centrally by transverse furrow. Second tergite 1.2 times as long as posteriorly wide; heavily rugose, with transverse impressions originating at about middle of tergite, sloping posteriorly, meeting centrally, delimiting vaguely defined rhombic area centrally; thyridia present. Third tergite with rugose/strigose sculpture, sculpture towards posterior edge smoother, with transverse impressions originating at about middle of tergite, sloping anteriorly, meeting centrally. Posterior tergites slightly coriaceous. Ovipositor thin, straight, without dorsal notch; ovipositor sheaths short, concealed by large hypopygium.
Blackish-brown; flagellomeres brown, dull orange basally; face clypeus and malar space dull yellow/pale orange, frons fuscous, vertex with creamy orbital marks between eyes and ocelli, small pale area behind subocular sulcus; indistinct reddish-brown patches at anterolateral margins and whole course of notauli (if they were impressed), scutellum brown; propleuron, ventrally on pronotum and lower third of mesopleuron pale orange; legs basically dull yellow/orange, narrow basal band on hind tibia dark brown, fore and mid coxa, all trochanters and trochantelli pale. Tergites dark brown, second and third tergites narrowly dull orange apically. Sternites creamy with yellow more sclerotized patches.
Comparison. Compared with the other species that have densely setose eyes, it is much larger, the mesoscutum with reddish bars along notauli, antennae comparatively long, with Description. Female. Fore wing length 2.6 mm. Face at level of antennal sockets 1.1 times as wide as high; face matt, finely and densely pustulate, frons finely pustulate with hairs, temples with fine matt-like coriaceous sculpture; eyes setose; dorsal ridge of face in between antennal sockets without a median prominence; face in profile almost straight, slightly impressed dorsally, edge of clypeus straight, antennal sockets on a high shelf; subocular sulcus distinct, sharp, bent towards occiput; maxillary palp reaching to about epicnemial carina. Head in dorsal view posteriorly deeply concave, temples distinct, lateral ocellus separated from eye by a distance 2 times 1.3 times longer than its maximum diameter, POL 0.9 times as long as diameter of lateral ocellus, ocellar-ocular grooves lacking. Minimum distance between antennal sockets very narrow, sockets almost touching each other; antenna short, moniliform, with 24 transverse flagellomeres, apical flagellomeres subquadrate, first flagellomere 0.8 times as long as wide and about 1/3 of the scape length, scape nearly parallel-sided.
Wings not particularly narrow; fore wing with areolet closed, areolet comparatively large, about as high as wide, 2m-cu meeting areolet at apical 0.7, vein Rs straight; nervellus not intercepted, gently curved.
Body largely setose except pronotum, mesopleuron and metapleuron; setae few and scattered on propodeum and posterior sides of coxae.
Dark brown except mouthparts, upper margin of face and small marks between inner orbits and antennal sockets, fore and mid legs, tegula, light yellow; sternites creamy, propleuron ventrally, legs largely except dorsal half of hind coxa and hind femur dorsally yellow; division of dark and pale colours blurred.
Male. Unknown. Biology. Hosts unknown. Etymology. Named from the Greek τρίχα (hair) and οπτικθσ (optics, eye) after the relatively dense setae on the surface of the eyes.
Comparison. Compared with the other species that have densely setose eyes, the face, mesoscutum, propleuron and mesopleuron are fuscous, the subocular sulcus distinct, the antennae comparatively short with 24 flagellomeres, unlike in O.  Distribution. Holarctic; *South Korea (GB, GW), *Japan.

Discussion
Altogether 25 species of Orthocentrus are found to occur in South Korea, previously none of these had been reported from this country, and neither had the genus Orthocentrus. Among them, 15 species are new to science and 10 are known species of Palaearctic or Holarctic distribution. After this work, the Korean fauna of Orthocentrus can be considered the best studied in the East Palaearctic. Unfortunately not all the available males were associated with specific females, and probably the use of molecular methods could help to solve this problem in a future study. All of the scarce reliable observations of Orthocentrus hosts are restricted to the genera Sciophila Meigen and Neoempheria Osten Sacken (Diptera, Mycetophilidae): O. asper was reared from Sciophila lutea Macquart (Šedivý and Ševčik 2003), O. protervus from Sciophila hirta Mg. (Roman 1923), O. stigmaticus from Sciophila rufa Mg. (Kolarov 1986), and unidentified Orthocentrus species from Neoempheria carinata Sueyoshi (Mukai and Kitajima 2019). No biological information concerning Orthocentrus hosts is available from South Korea. Veijalainen et al. (2014), after studying Orthocentrus in the Neotropics, concluded that the genus is not monophyletic and perhaps should be divided. They proposed five speciesgroups, and some of them (e.g. O. maculae and O. shieldsi species-groups), could be found also in the Palaearctic fauna. We agree with their opinion in general; however, to address the possible split of Orthocentrus, a more comprehensive analysis is needed, ideally including specimens from all regions of the world. For the moment, this division could not be applied to the Palaearctic species of the genus, as many distinctive characters overlap and consequently the species-group definitions do not fit well to many species from our study.
Orthocentrinae still remains an incompletely investigated group if compared with other ichneumonid subfamilies and requires much more taxonomic attention; however, the efforts of several researchers resulted in some progress in this field during the last few decades. Despite this the number of unknown Orthocentrinae species remains very high, especially in the tropical regions.