Four new species of Closterocerus Westwood (Hymenoptera, Eulophidae) from China, with a key to Chinese species

Abstract Four new species of Closterocerus Westwood, C. rectisulcussp. nov., C. shaanxiensissp. nov., C. separatussp. nov. and C. unifasciatussp. nov. are described from China, each with a distinct pattern on the fore wings, and belonging to subgenus Closterocerus. A key to all species of the genus Closterocerus in China is provided.

parts of the world possibly belong to the subgenus Closterocerus, but the descriptions lack the character Hansson (1994) used to characterize the subgenus.
In the present paper, we describe four new species of the subgenus Closterocerus s. str. from China, each with a distinct pattern on the fore wing, and a key to all species of the genus Closterocerus distributed in China is provided.

Material and methods
Specimens were collected by sweeping, and were dissected and mounted in Canada Balsam on slides following the method of Noyes (1982), or mounted on a card. Photos were taken with a digital CCD camera attached to an Olympus BX51 compound microscope or Aosvi AO-HK830-5870T digital microscope. Measurements were made using an eye-piece reticle, or using the ruler tool in Adobe Photoshop 2020.
Terminology follows the Hymenoptera Anatomy Consortium (2020), and the following abbreviations are used: Scape slightly compressed, widest in middle part; F3 wider than F2 (Fig. 31)  Propodeal plica absent, spiracular sulcus present (Fig. 6); transverse V-shaped band at apex of fore wing dark and distinct (Fig. 7) (Fig. 7): band I V-shaped, with upper arm longer and more distinct than lower arm; band II obscure medially or nearly interrupted; band III V-shaped, with upper arm slightly longer than lower arm; the three bands are nearly connected in the middle; stigmal hairline absent, radial cell setose; below base of cubital setal line with five setae in a row; propodeum with a short median carina delimited by a transverse carina posteriorly; propodeal plica absent; spiracular sulcus present.
Description. Female. Length 0.9-1.3 mm. Scape and pedicel dark brown to black. Flagellum dark brown to pale brown, becoming gradually paler distad. Eyes red, ocelli pale brown. Vertex and frons above frontal sulcus golden-green to golden-blue. Frons below frontal sulcus golden-yellow to golden-green. Mandibles pale brown. Pronotal collar, mesoscutum, mesoscutellum and axillae golden-green in dorsal view, golden-blue in lateral view. Metascutellum and propodeum dark bronze. Fore wing ( Fig. 7) with three infuscate transverse bands: band I (below the middle of MV) V-shaped, with upper arm longer and more distinct than lower arm; band II (below STV), obscure medially or nearly interrupted; band III (at apical margin of fore wing) V-shaped, with upper arm slightly longer than lower arm; the three bands are nearly connected in middle. All coxae, femora and tarsal claws dark brown (metacoxae darker, nearly black); trochanters pale brown; protibiae and mesotibiae mainly pale yellow, slightly pale brown basally; metatibiae dark brown; pro-and mesotarsi pale yellow with last tarsomere pale brown; metatarsi pale yellow with last tarsomere dark brown. Metasoma dark brown with weak metallic bluish-green to bronze reflections.  to the extremely compressed scape, slightly shorter than wide (ca 4 : 5). Flagellum extremely compressed; F1-3 wider than long, F2 longer and wider than F1 and F3; F4 quadrate; F5 small, tapering distad, with terminal spine shorter than the segment.
Mesosoma (Figs 3, 6). Pronotum, mesoscutum, mesoscutellum, axillae and posterior part of propodeum with reticulate sculpture, meshes nearly of same size (but wider on mesoscutellum). Metascutellum with irregular rugae. Pronotum transverse, invisible in dorsal view. Median area of mesoscutum with two pairs of setae. Notauli curved in anterior part, and indicated posteriorly by depression. Mesoscutellum 0.97 times as long as wide. Axillae slightly advanced forwards in front of level of anterior margin of mesoscutellum. Mesoscutum and mesoscutellum slightly convex. Metascutellum about 1/3 as long as median length of propodeum. Propodeum with a short median carina delimited by a transverse carina posteriorly. Propodeal plica absent, spiracular sulcus present. Fore wing (Fig. 7) about twice as long as wide, without stigmal hairline, radial cell setose. Speculum closed below. Ratio length of: SMV : MV : PMV : STV about 3 : 6 : 1 : 1. Cubital setal line straight and completely extending to base of MV. Below base of cubital setal line with five setae in a row. Hind wing (Fig. 7) about 4.5 times as long as wide. Legs ( Fig. 9) with all coxae reticulate on outer surface; ventral margin of pro-and metafemur with six and ten long setae respectively; mesotibial spur about 0.9 times as long as corresponding basitarsus.
Male. Unknown. Host. Unknown. Etymology. The name refers to the straight frontal sulcus in this species (rectus is Latin for straight).
Distribution. China (Heilongjiang, Liaoning, Shaanxi provinces). Remarks. Closterocerus rectisulcus sp. nov. is similar to C. orientalis Yefremova & Kriskovich, 1996 because they share a similar pattern of the fore wing according to the description. The new species differs as follows: pedicel slightly shorter than, or at most as long as wide (longer than wide in C. orientalis); mesoscutellum approx. as long as wide (three times as long as wide in C. orientalis); mesotibial spur 0.9 times as long as corresponding basitarsus (1.7 times as long as corresponding basitarsus in C. orientalis). Diagnosis. Frontal sulcus straight, reaching eye margins; fore wing with band I V-shaped, with upper arm much longer and darker than lower arm, the lower arm obscure; band II distinct and interrupted medially; band III V-shaped, obscure, much paler than band I and II, with upper arm slightly longer than lower arm; the three bands are separated from each other; fore wing without stigmal hairline, radial cell setose; below base of cubital setal line with nine setae in a row; propodeal plica present, spiracular sulcus absent.

Closterocerus shaanxiensis
Description. Female. Length 1.1-1.3 mm. Scape and pedicel dark brown to black. Flagellum dark brown to pale brown, becoming gradually paler distad. Eyes red, ocelli pale brown to red. Vertex and frons above frontal sulcus golden-green to goldenblue. Frons below frontal sulcus mainly golden-yellow with golden-green tinge. Pronotal collar, mesoscutum, mesoscutellum and axillae golden-green to golden-yellow in dorsal view, golden-blue in lateral view. Metanotum and propodeum brown, without metallic reflections, except the median part of metascutellum concolorous with mesoscutellum. Fore wing (Fig. 16) with band I V-shaped, with upper arm much longer and darker than lower arm, the lower arm much obscure; band II distinct and interrupted medially; band III V-shaped, obscure, much paler than the band I and II, with upper arm slightly longer than lower arm; the three are separated from each other. Legs with all coxae, femora and tarsal claws dark brown; trochanters pale brown; protibiae main- ly pale yellow, pale brown basally; mesotibiae with basal half pale brown and apical half pale yellow; metatibiae dark brown; tarsi pale yellow with last tarsomere pale brown to brown. Metasoma brown with rather weak reflections.
Head (Figs 11,12), in frontal view 1.45 times as wide as high. Sculpture on vertex and frons above frontal sulcus nearly with the same sized meshes. POL : OOL = 6 : 5. Frontal sulcus straight, reaching eye margins; inner eye margins slightly concave in lower part. Antennal scrobes join on frontal sulcus. Malar sulcus absent, but with a curved transverse carina near clypeus, extending to lower margin of eyes. Clypeus not delimited. HE : MS : WM about 3.9 : 1.0 : 2.2. Antenna (Fig. 13) inserted slightly above level of lower margin of eyes. Scape reticulate, extremely compressed, and expanded from base to apex, about 2.2 times as long as wide. Pedicel moderately compressed compared to the extremely compressed scape, slightly longer than wide (about 9 : 8). Flagellum extremely compressed; F1 wider than long; F2 and F3 quadrate; F4 slightly longer than wide; F2 widest and longest and gradually tapering from F2 to F5; F5 with terminal spine shorter than the segment.
Mesosoma (Figs 14, 15). Pronotum, mesoscutum, mesoscutellum and axillae with reticulate sculpture, meshes nearly of same size. Metascutellum with irregular rugae. Pronotum transverse, invisible in dorsal view. Median area of mesoscutal midlobe with two pairs of setae. Notauli curved in anterior part, and indicated posteriorly by depression. Mesoscutellum approx. as long as wide. Axillae slightly advanced forwards in front of level of anterior margin of mesoscutellum. Mesoscutum and mesoscutellum slightly convex. Metascutellum about 3/5 as long as median length of propodeum. Propodeum without reticulate sculpture, with a short median carina delimited by a transverse carina posteriorly. Propodeal plica present, spiracular sulcus absent. Fore wing (Fig. 16) about twice as long as wide, without stigmal hairline, radial cell setose. Speculum closed below. Ratio length of: SMV : MV : PMV : STV about 4 : 8 : 1 : 1. Cubital setal line straight and completely extending to base of MV. Below base of cubital setal line with nine setae in a row. Hind wing (Fig. 16) about 4.5 times as long as wide. Legs (Fig. 18) normal.
Male. Unknown. Host. Unknown. Etymology. The specific name is derived from the name of the collection locality, Shaanxi Province.
Distribution. China (Shaanxi Province). Remarks. Closterocerus shaanxiensis sp. nov. is similar to C. rectisulcus sp. nov., but differs as follows: fore wing below base of cubital setal line with nine setae in a row (five in C. rectisulcus); propodeum smooth, without reticulate sculpture (with reticulate sculpture posteriorly in C. rectisulcus); propodeal plica present (absent in C. rectisulcus); spiracular sulcus absent (present in C. rectisulcus). The pattern on the fore wing and color of the metasoma are also different from that in C. rectisulcus: band III obscure, much paler than band I and II; the three bands are separated from each other (in C. rectisulcus, band III distinct, only slightly paler than band I and II; the three bands are nearly connected in the middle); metasoma brown (dark brown in C. rectisulcus). Diagnosis. Female. Head, in frontal view, oval, 1.4 times as wide as high; scape strongly compressed, and extremely expanded distad, 2.4 times as long as wide; fore wing with band I replaced by an obscure infuscate cloud; band II obvious, reaching hind margin of fore wing; band III extended along apical margin, obvious, slightly protruded inwards medially; the cloud and two bands are separated from each other; between cubital setal line and the hind margin of fore wing with a longitudinal infuscation; ventral margin of metafemur with six long setae.

Closterocerus separatus
Description. Female. Length 1.06-1.15 mm. Antennae dark brown. Eyes and ocelli dull red. Frons golden-yellow to golden-green. Vertex golden-green in dorsal view, golden-blue in lateral view and frontal view. Mandibles pale brown. Pronotal collar, mesoscutum, mesoscutellum, axillae and metascutellum golden-green in dorsal view, golden-blue in lateral view. Propodeum, mesopleuron and metapleuron brown, dark brown to black. Legs with all coxae, femora and tarsal claws dark brown; pro-and mesotrochanters pale brown, metatrochanters dark brown; protibiae mainly pale yellow, pale brown basally; mesotibiae mainly pale yellow; metatibiae dark brown; all tarsi pale yellow, but first segment of metatarsi dark brown. Fore wing (Fig. 25)  cloud and two bands are separated from each other; between cubital setal line and the hind margin of fore wing with a longitudinal infuscation. Metasoma dark brown with weak metallic green to blue reflections.
Head (Figs 20,22), oval in frontal view, 1.4 times as wide as high. Meshes of reticulate sculpture on vertex and frons below frontal sulcus smaller than that on frons above frontal sulcus. POL : OOL = 5 : 4. Frontal sulcus V-shaped, reaching eye mar- gins; inner eye margins concave medially. Antennal scrobes join on the frontal sulcus. Malar sulcus absent, but with a curved transverse carina near clypeus, extending to lower margin of eyes. Clypeus not delimited. HE : MS : WM about 4.0 : 1.0 : 2.0. Antenna (Fig. 23) inserted above level of lower margin of eyes. Scape strongly compressed, and extremely expanded distad, 2.4 times as long as wide. Pedicel moderately compressed compared to the extremely compressed scape, nearly as long as wide. Flagellum extremely compressed; F1-4 wider than long, F2 slightly larger than F1 and F3; F3 wider than F4; F5 small, almost oval, with terminal spine long and nearly as long as the segment.
Mesosoma (Figs 21, 24). Pronotum, mesoscutum, axillae and mesoscutellum (except posterior margin) with reticulate sculpture, meshes nearly of same size. Metascutellum and propodeum smooth. Along pronotal collar with four strong setae. Median area of midlobe of mesoscutum with three pairs of setae. Notauli curved in anterior part, and indicated posteriorly by depression. Mesoscutellum as long as wide. Axillae slightly advanced forwards in front of level of anterior margin of mesoscutellum. Mesoscutum and mesoscutellum rather flat. Metascutellum large, about half median length of propodeum. Propodeum without any carina in middle part. Fore wing (Fig. 25) twice as long as wide, with a stigmal hairline, radial cell bare. Speculum nearly elongate-triangular, closed below. Ratio length of: SMV : MV : PMV : STV about 5 : 11 : 1 : 2. Cubital setal line straight and completely extending to base of MV. Hind wing (Fig. 25) narrow, about 6.2 times as long as wide. Legs (Fig. 27) normal, with all coxae reticulate on outer surfaces; ventral margin of metafemur with six long setae.
Male. Unknown. Host. Unknown. Etymology. The name refers to the separated distal two cross bands of fore wing (separatus is Latin for separate).
Distribution. China (Heilongjiang, Hebei provinces). Remarks. Closterocerus separatus sp. nov. is similar to C. africanus Waterston, 1925, C. cruy (Girault, 1918) and C. mirabilis Edwards & La Salle, 2004, according to the original descriptions. They share the following characters with the new species: fore wing with an infuscate cloud and two infuscate bands; between cubital setal line and the hind margin of fore wing with a longitudinal infuscation; but the new species differs from C. africanus by having the head 1.4 times as wide as high in frontal view (1.6 times in C. africanus); ventral margin of metafemur with six long setae (ten setae in C. africanus); the area between infuscate cloud and band II of fore wing hyaline (slightly infuscate in C. africanus). The new species differs from C. cruy and C. mirabilis in having the infuscate cloud and two bands on the fore wing separated from each other (the cloud is distinctly connected with band II, and band III is nearly connected with band II in C. mirabilis; band II is distinctly connected to the cloud and bands III in C. cruy); apex of scape wider, about 0.4 times as wide as the length of scape (at most 0.3 times in C. cruy and C. mirabilis). Diagnosis. Face near clypeus with a curved, nearly V-shaped transverse carina; clypeus delimited laterally; F4 widest; fore wing with band I absent; band II becoming paler and wider posteriorly; band III extending along apical margin, much obscure (nearly imperceptible on slide); propodeum smooth and shiny, without any carina, spiracular sulcus present.