Review of the genus Syzeuctus (Hymenoptera, Ichneumonidae, Banchinae) from South Korea

Only two species (Syzeuctus coreanus and S. sambonis) of the genus Syzeuctus were known to inhabit South Korea. In the present study, four species of this genus are newly recorded from South Korea. Among them, two species, S. albopictus Kang & Lee, sp. nov. and S. flavofacialis Kang & Lee, sp. nov., are described as new. Of the other species, the male of S. takaozanus was hitherto unknown and is described here, and S. apicifer is also new to South Korea. A key to these South Korean species along with the descriptions of the two newly recorded species and digital images are provided.


Introduction
The genus Syzeuctus Förster is one of the large genera of the tribe Atrophini, subfamily Banchinae, and comprises 123 species ). Among them, only 14 species inhabit the Eastern Palearctic region, and two species (Syzeuctus coreanus Uchida and S. sambonis Uchida) were recorded in South Korea. This genus can be distinguished from other genera of the tribe by the following characteristics: frons often with a horn, ridge, or tooth above each antennal socket; genal carina reaching base of mandible; small and triangular areolet with a long stalk. Species of this genus are koinobiont endoparasitoids of Lepidoptera larvae, especially Pyralidae ).
In the present study, we report two species new for science (Syzeuctus albopictus Kang & Lee, sp. nov. and S. flavofacialis Kang & Lee, sp. nov.) and two species newly recorded from South Korea (S. apicifer and S. takaozanus). Digital images of the new species and newly recorded species along with a key to the South Korean species of Syzeuctus are provided.

Materials and methods
The wasps investigated in this study were collected by sweep net and by Malaise traps and deposited in the Georim Entomological Institute (Daegu, South Korea). Distributional data follow Yu et al. (2016). Abbreviations used in the text are as follows.

GEI
Georim Entomological Institute, Daegu, South Korea HU Hokkaido University, Faculty of Agriculture, Entomological Institute, Sapporo, Japan NHMUK The Natural History Museum, Type depository TL Type locality Specimens were examined using an AxioCam MRc5 camera attached to a stereo microscope (Zeiss SteREO Discovery. V20; Carl Zeiss, Göttingen, Germany), processed using the AxioVision SE64 software (Carl Zeiss), and optimized with a Delta imaging system (i-solution, IMT i-Solution Inc., Vancouver, Canada). Mor phological terminology is applied according to the American Entomological Institute website (http://www.amentinst.org/GIN/morphology.php). Diagnosis. Fore wing 5.0 -14.0 mm. Body of moderate proportion to rather slender, the mesosoma usually short. Apex of clypeus in general convex but often truncate or less strongly convex apically. Occipital carina reaching base of mandible. Epomia long and strong. Areolet rather small, triangular with a long stalk, receiving second recurrent vein distad of middle. First tergite rather short, polished with rather sparse to very sparse punctures, moderately tapered toward base. Ovipositor sheath 1.5 to 3.0 times as long as hind tibia (Townes 1970).

Order Hymenoptera
Key to the South Korean species of Syzeuctus  (Fig. 1A), fore wing 8.0 mm in length. Head in dorsal view with temple narrowed at an angle of more than 45° (Fig. 1C), strongly rounded. Face strongly convex, densely and coarsely punctate, with strong median swelling and two lateral swellings above clypeal fovea. Clypeus convex, with long and thin setae; convex apically; clypeal fovea small, open. Mandible slightly tapered, upper tooth slightly longer than lower tooth; lower ridge lamelliform. Maxillary palp with five segments. Frons smooth and concave with small dense punctures. Vertex more sparsely punctate than face. Occipital carina complete, slightly sinuous, joining hypostomal carina at mandibular base. Temple polished and convex with fine punctures. Malar space about 1.3 times as long as basal mandibular width. Inner margin of eye parallel. Antenna filiform with 49 flagellomeres; first flagellomere 3.8 times as long as its width, 1.5 times as long as second flagellomere.
Color whitish yellow. Head whitish yellow with brown marks. Mandibular teeth brown (Fig. 1B). Frons and vertex with brown mark around ocellar triangle. Antenna yellow. Mesoscutum brown with triangular whitish yellow spot on its anterior on both sides. Scutellum yellowish brown. Postscutellum whitish yellow. Anterior margin of pronotum dorsally with brown mark. Mesopleuron with yellowish brown mark. Propodeum in dorsal view with elongate brown mark on each side of its anterior part (Fig. 1E). Legs entirely whitish yellow. Hind tarsal claw bright brown. Wings hyaline (Fig. 1G). Metasoma whitish yellow with yellowish brown coloration posteriorly (Fig. 1H).

Distribution. South Korea (new record).
Remark. This species is easily distinguished by its very bright body color and very long malar space, 1.3 times the basal mandibular width. Diagnosis. Female. Face convex, densely and coarsely punctate. Clypeus truncate apically. Temple polished and convex, with fine punctures. Malar space about 0.7 times as long as basal mandibular width. Antenna filiform with 43 flagellomeres; first flagellomere 1.8 times as long as second flagellomere. Mesosoma stout with dense pubescence. Epicnemium with a developed lamelliform projection apically. Propodeum in dorsal view stout; closely punctate tending to rugose, partly with dense setae; without posterior transverse carina. Fore and mid tarsal claws pectinate. Ratio of hind tarsal segments are 4.5: 2.5: 1.6: 0.8: 1.0; hind tarsal claw simple. Hind wing with eight hamuli. First tergite rectangular, 2.5 times as long as posterior width, without lateral longitudinal carina. Second tergite coriaceous, 1.5 times as long as posterior width. Ovipositor sheath with dense, short setae; approximately as long as metasoma.

Syzeuctus apicifer (Walker, 1874)
Color. Black with brownish metasoma. Frontal orbit yellow, interrupted medially. Clypeus and mandible yellow with black mandibular teeth. Genal orbit yellow. Malar space yellow apically. Antenna brown with black scape and pedicel. Mesoscutum black with a small anterior triangular yellow spot on each side. Scutellum yellow except black triangular spot anteriorly. Tegula yellow. Mesopleuron black with small yellow mark just below tegula. Upper projection of mesepimeron yellow. Propodeum in dorsal view with small yellow spot on each side of anterior part; strongly pointed triangular mark posteriorly. Fore wing with brown spot apically. Fore and mid legs entirely yellow with brown tarsal claw. Hind coxa and trochanter black with brown apically; trochantellus yellow; femur yellowish brown; tarsus and tarsal claw tan brown. Metasoma brown with black posteriorly. First tergite with yellow anteriorly and posteriorly.
Male. Male has more yellow spots; face, pronotum with longitudinal mark anteriorly and upper and posterior corner, mesopleuron with a longitudinal mark, posterior half of metapleuron. The color of genal orbit, mesoscutum, scutellum, propodeum are same with female. First and Second tergite black with yellow anteriorly and posteriorly. Third and fourth tergites brown with yellow posteriorly. Fore wing a bit infuscate apically, without spot. Description. Female. Body 10.0 mm in length. Fore wing 7.0 mm in length (Fig. 3A). Head in dorsal view flat with temple narrowed at an angle of more than 45°, round (Fig. 3C). Face convex, densely and coarsely punctate; with median swelling and two lateral swellings above clypeal fovea (Fig. 3B). Clypeus flat, with long and strong setae; apically truncate; clypeal fovea open. Mandible moderately stout, strongly tapered, upper tooth slightly longer than lower tooth; lower ridge strongly developed, lamelliform. Maxillary palp with five segments. Frons smooth, convex, with small dense punctures. Vertex more sparsely punctate than face. Occipital carina complete, slightly sinuous, joining hypostomal carina at mandibular base. Temple polished and convex, with fine punctures. Malar space about 0.5 times as long as basal mandibular width. Inner margins of eyes parallel. Antenna filiform with 42 flagellomeres; first flagellomere 4.5 times as long as its width, 1.6 times as long as second flagellomere.
Metasoma depressed with shallow and dense punctures (Fig. 3H). First tergite rectangular, 1.8 times as long as posterior width, without lateral longitudinal carina (Fig. 3F). Second tergite coriaceous, 1.2 times as long as posterior width. Ovipositor sheath with dense, short setae, 1.6 times as long as metasoma, 4.0 times as long as hind tibia.
Color black with yellow marks. Head black. Face yellow with black median longitudinal mark (Fig. 3B); area around clypeal fovea black. Mandibular teeth black. Frontal orbit and genal orbit broadly yellow. Malar space yellow. Antenna brown; scape black with brown ventrally; pedicel yellow. Mesosoma black with yellow marks (Fig. 3D). Mesoscutum black with anterior triangular yellow spot on each side; medially with big yellow spot. Scutellum entirely yellow. Upper margin of pronotum broadly yellow; lower anterior margin with yellow spot. Tegula yellow. Mesopleuron black with yellow upper margin and lower posterior margin, slightly above middle with short yellow short boomerang-shaped mark. Propodeum in dorsal view with yellow spot on each side of anterior part; triangular yellow mark posteriorly (Fig. 3E). Fore and mid legs bright yellow with brown apex of mid tarsus and tarsal claw. Hind coxa and trochanter black; trochantellus yellow; femur bright brown; all tarsal segments yellow with black each apically; tarsal claw black. Wings weakly infuscate (Fig. 3G). Metasoma black. First tergite black with yellow anterior third; first to fourth tergites each with a posterior yellow line (Fig. 3H) Remark. This species is similar to S. sambonis in that its face is convex, but unlike S. sambonis, which has a face that is convex overall, S. flavofacialis has median and lateral swellings.  Uchida, 1928 Fig. 4 Syzeuctus takaozanus Uchida, 1928: 95. Lectotype: ♀, TL: Japan, TD: HU.

Syzeuctus takaozanus
Description. Male. Body 13.0 mm in length. Fore wing 8.0 mm in length (Fig. 4A). Head in dorsal view flat with temple narrowed at an angle of about 45°, round (Fig. 4C). Face convex, densely and coarsely punctate, without swelling. Clypeus flat, with long and thin setae, apically convex (Fig. 4B); clypeal fovea open. Mandible moderately stout, strongly tapered, upper tooth slightly longer than lower tooth; lower ridge not developed. Maxillary palp with five segments. Frons smooth and convex with dense punctures. Vertex more sparsely and finely punctate than face. Occipital carina complete, slightly sinuous, joining hypostomal carina at mandibular base. Temple polished and convex with fine punctures. Malar space about 0.6 times as long as basal mandibular width. Inner margin of eye parallel. Antenna filiform with 42 flagellomeres; first flagellomere 3.0 times as long as its width, 2.0 times as long as second flagellomere.