Review of Dibrachys Förster from China (Hymenoptera, Chalcidoidea, Pteromalidae)

Abstract Twelve species of Dibrachys Förster are studied from China, of which four new species, Dibrachys golmudica Jiao & Xiao, sp. n., Dibrachys kunmingica Jiao & Xiao, sp. n., Dibrachys liaoi Jiao & Xiao, sp. n. and Dibrachys qinghaiensis Jiao & Xiao, sp. n., and four newly recorded species, Dibrachys braconidis (Ferrière & Faure), Dibrachys confusus (Girault), Dibrachys hians Bouček and Dibrachys maculipennis Szelényi, are reported. A key to Chinese Dibrachys and illustrations of external features of the species are provided.


Introduction
Dibrachys was erected by Förster in 1856, but without any species included in the genus. Thomson (1878) subsequently designated Pteromalus boucheanus Ratzeburg, 1844 as the type species and listed Pteromalus cavus Walker, 1835 as a synonym. Although the type material of P. boucheanus is lost (Graham 1969), Thomson's work was accepted by the majority of later researchers. Graham (1969) designated a lectotype for P. cavus and suggested that, failing the discovery of the type material of P. boucheanus, the lectotype of P. cavus might conveniently be made also the neotype of P. boucheanus because the two were supposed to be identical. However, Peters and Baur (2011) designated a different specimen as lectotype as part of their review of the Dibrachys cavus species complex, in which they treated Dibrachys cavus as a junior synonym of Dibrachys microgastri (Bouché, 1834). Consequently, D. microgastri (Bouché) is the senior synonym of both D. boucheanus (Ratzeburg) and D. cavus (Walker).
Based on differences in mandibular formula and fore wing marginal fringe, Bouček (1965) divided the genus into two subgenera Dibrachys Förster s. str. and D. (Allodibrachys Bouček). Nineteen valid species of Dibrachys are recognized, of which 13 are known from the Palearctic region, 8 from the Nearctic region, 4 from the Oriental region, 1 from the Australasian region, 1 from the Afrotropical region and 2 from the Neotropical region (Noyes 2016). Most species are parasitoids of insect pests, and play an important role in biological control, with 372 different host species being reported for Dibrachys (Grissell 1974;Noyes 2016), including species of Lepidoptera, Hymenoptera, Diptera, Coleoptera, Dermaptera, Hemiptera, Neuroptera, Strepsiptera, and several species of Arachnida (Araneidae and Philodromidae). However, as Graham (1969) noted, almost all the host records are associated with D. cavus.

Material and methods
A total of 943 specimens was examined from the museum of Institute of Zoology, the Chinese Academy of Sciences (IZCAS). All material from our own collection was swept and preserved in 75% ethanol. Specimens were subsequently air dried, pointmounted and examined with a Nikon SMZ1500 stereomicroscope. Photographs were taken using a Nikon Multizoom AZ100 system, and the plates were compiled using Adobe Photoshop CS3 software. In addition, the author had examined specimens of Dibrachys deposited in the National History Museum, London, the Naturalis, Leiden and the Bavarian State Collections of Zoology in April, 2002. Morphological terminology mostly follows that of Graham (1969), Bouček (1988) and Gibson (1997). All specimens were examined and identified using the keys of Graham (1969), Grissell (1974), Doganlar (1987), Yang (1996), Zerova et al (1992) and Peters and Baur (2011). Every new species is described based on the holotype specimen, other species are described basing on the examined material available to us. Body length excludes the ovipositor sheaths and is measured in millimeters (mm); other measurements are given as ratios.  Graham 1969: 804-814;Wallace 1973: 175-176;Bouček 1993Bouček : 1259Yang 1996: 196-201, 323-324. Coelopisthoidea Gahan, 1913. Type-species: Coelopisthoidea cladiae Gahan, 1913: 178-183. Synonymized by Girault 1916bBouček 1988: 434. Diagnosis. Body dark green. Head in frontal view round; antennal insertion placed on lower ocular line and face not protuberant at antennal insertion; antennal formula 11263 (rarely 11353); lower margin of clypeus with two sinuate teeth; both mandibles with four teeth or right mandible with four teeth and left mandible with three teeth; head in dorsal view with occiput margined by blunt or sharp, transverse ridge. Mesosoma slightly convex; pronotal collar not margined or slightly carinate medially; notauli incomplete and inconspicuous; scutellum without frenal groove; propodeum with plica complete, median carina developed or not. Fore wing without marginal fringe or at least bare between postmarginal vein and wing apex; postmarginal vein short, only inconspicuously longer than stigmal vein. Hind tibia with one spur. Gaster ovate.
Hosts. Yang (1996) reported this species as reared from the pupae of some chalcid collected from tunnels in Picea koraiensis Nakai (Pinales: Pinaceae) built by the wood pest Orthotomicus golovjankoi Pjatnitzky (Coleoptera: Curculionidae), the possible host.
Distribution. China (Heilongjiang). Diagnosis. The species belongs to subgenus Allodibrachys, and similar to D. yunnanensis Yang has the lower angle of the gena not exceeding the clypeal margin, and the stigmal vein slightly shorter than the postmarginal vein. The main differences are:
Head in frontal view (Fig. 12), width 1.29× height; frons with irregular reticulation, lower face curved ventrally; eye height 0.68× head height, inner margin of eyes slightly converging upwards, separated by 1.24× their height; antennal scrope deep, not reaching anterior ocellus; reticulation in antennal scrobe smaller than that on parascrobe. Antennal insertion slightly above lower ocular line, distance from upper margin of antennal torulus to lower margin of anterior ocellus 2× distance from lower margin of antennal torulus to clypeal margin; clypeus with dense longitudinal striation; clypeal margin slightly protruded, emarginate in the middle and with two blunt teeth, median margin concave, as a small, smooth, triangular depression; gena plump, oral fossa 0.48× as wide as head. Head in lateral view with malar sulcus inconspicuous, eye height 2.2× malar space. Antennal scape length 0.83× eye height, not reaching anterior ocellus; pedicel in lateral view 2.5× as long as broad; both anelli transverse. Head in dorsal view (Fig. 13), head 2× as wide as long; vertex convex, with regular reticulation denser than that on frons, posterior part sharply sloped down; eye length 2× temple length; POL 1.6× OOL.
Head 1.19× as broad as thorax. Mesosoma 1.37× as long as broad. Propodeum with short collar, collar subhorizontal and not margined, posterior margin smooth. Mesoscutum 2× as broad as long, reticulation on posterior area bigger than that on anterior area. Scutellum slightly convex medially, width 1.22× length, frenal line absent; reticulation shallower than that on mesoscutum posteriorly. Median length of propodeum half that of scutellum; median area flat, with deep, fine, dense reticulation; median carina absent; plica incomplete, visible anteriorly; plicae separated by 1.68× median length of propodeum; short nucha hemispheric and smooth; spiracles elongate, 2× as long as broad, separated from hind margin of metanotum by width of spiracle. Fore wing (Fig. 14) 2.36× as long as broad; without fringe from postmarginal vein to distal margin; hind wing with marginal fringe; basal vein and basal cell bare, speculum only extending to base of marginal vein; upper surface of costal cell bare, lower surface with one compact row of setae and distal 1/3 with one row of short setae and some scattered setae; submarginal vein 2× as long as marginal vein; marginal vein 1.91× as long as postmarginal vein, 2× as long as stigma vein; stigmal vein slightly shorter than postmarginal vein (0.96×); stigmal vein curved.
Petiole quadrate, as long as broad. Gaster (Fig. 10)   Etymology. Named after the location of the type material. Hosts. Unknown. Distribution. China (Yunnan).

Dibrachys yunnanensis Yang, 1996
Dibrachys yunnanensis Yang, 1996: 199-201, 324. Diagnosis. Body squat, length 2.0-2.4 mm. Head in front view 1.3× as wide as high; antennal scrobe shallow, extending upwards and reaching anterior ocellus; antennal insertion placed on the lower ocular line; clypeus with longitudinal sculpture; lower margin of clypeus slightly protruded, median emarginate and with 2 sinuate teeth; gena evenly curved, lower angle of gena not exceeding clypeal margin. Antennal scape slightly shorter than eye height, length of flagellum and pedicel combined less than head width (0.74×); pedicel in lateral view 2.2× as long as broad; both anelli transverse; Fu 1 and Fu 5 quadrate, Fu 6 distinctly transverse. Head in dorsal view, 1.9× as wide as long, eye length 1.79× temple length; POL 1.78× OOL. Mesosoma 1.5× as long as broad, mid lobe of mesoscutum with regular sculpture. Propodeum with plicae complete, median carina distinct on base part. Fore wing with submarginal vein more than 2× as long as marginal vein, marginal vein 1.5× as long as postmarginal vein, stigmal vein as long as postmarginal vein. Gaster 1.3× as long as broad, as broad as thorax width.

Dibrachys (Dibrachys) Förster
Diagnosis. Both mandibles with four teeth; occipital carina curving, closer to vertex than foramen; fore wing without marginal fringe; gaster spindle-shaped, distinctly longer than broad. ( Distribution. China (Sichuan, Yunnan, Tibet); Palearctic and Nearctic regions. This is the first record from the Oriental region.
Head in frontal view (Fig. 25) 1.24× as wide as high; eyes with inner margins parallel, eye height 0.62× head height, eyes separated by 1.26× their height; lower face with weak striation, upper face with obvious regular reticulation; antennal scrobe deep, not reaching anterior ocellus. Antennal insertion on lower ocular line, distance from upper margin of torulus to lower margin of anterior ocellus 2.54× distance from lower margin of torulus to lower margin of clypeus; clypeus with longitudinal striation on both sides, lower margin slightly protruded, emarginate in middle with two obtuse teeth; oral fossa 0.49× as wide as head. Head in lateral view (Fig. 27) with malar sulcus conspicuous, eye height 1.5× its broad and 2.83× malar space. Antennal scape length 0.91× eye height; length of flagellum and pedicel combined less than head width (0.88×); pedicel in lateral view 2.3× as long as broad; antenna with 3 anelli, Fu 1 and Fu 2 distinctly transverse, Fu 3 quadrate, Fu 1 to Fu 3 combined 0.78× as long as pedicel; Fu 4 longer than broad, Fu 5 quadrate; each funicular segment with one row of sensilla; setae on funicle all decumbent; clava not distinctly clavate, 3.4× as long as broad, micropilosity limited to apex of third clava segment. Head in dorsal view (Fig. 26), 2× as wide as long; vertex convex, sculpture on vertex slightly smaller than sculpture on frons; occipital carina distinct; eye length 2.5× temple length; POL 2.11× OOL.
Head 1.24× as broad as thorax. Mesosoma 1.6× as long as broad. Pronotum 0.65× as broad as mesoscutum, collar rounded, posterior band smooth. Mesoscutum 1.57× as broad as long, with regular reticulation, in anterior half weakly reticulate and posterior half with deep reticulation; notauli distinct but not complete. Scutellum convex, 1.07× as broad as long, frenal line absent; reticulation smaller than on mesoscutum, but regular and shallow. Propodeum medially ½ as long as scutellum, with fine, deep, dense reticulation; plica weak ( Fig. 28), only visible basally and separated by 2× medial length of propodeum; median carina incomplete; propodeum with short, slightly convex nucha having transverse striation; propodeal spiracles elongate, 2.67× as long as broad. Fore wing 2.16× as long as broad, without marginal fringe; setae pale, inconspicuous; basal vein and basal cell bare, upper surface of costal cell bare, lower surface with one complete row of setae and distally with some scattered setae; submarginal vein 2.75× as long as marginal vein, marginal vein 2.63× as long as stigmal vein, postmarginal vein shorter than stigmal vein (at most 0.5×); stigmal vein slightly curved.
Male. Head black except frons with yellowish-green, and antennae yellow; mesosoma black except thorax purplish laterally, legs yellow except coxae brown. Antennae with two distinctly transverse anelli, pedicel in lateral view 1.8× as long as broad, each funicular segment longer than broad; gaster oval, apex not pointed.
Material Diagnosis. The new species belongs to Dibrachys s. str., and the mainly differences with Dibrachys microgastri (Bouché) as follows: D. liaoi sp. n. slightly blue-greenish, clypeal margin with two sharp teeth, Fu 1 to Fu 4 length slight longer than its width respectively, Fu 5 and Fu 6 quadrate, gaster 1.8× as long as broad; but in D. microgastri (Bouché), body yellow-green, clypeal margin with two blunt teeth, Fu 1 to Fu 5 quadrate, Fu 6 transverse, gaster 2× as long as broad. Description. Holotype. Female. Body (Figs 29, 30) length 2.2 mm. Head and mesosoma dark green, with metallic reflection; gaster brown and with metallic reflection basally. Antennae dark brown except scape and pedicel yellowish brown; mandible brown; legs yellowish brown except coxae brown; fore wing slightly infumate, wing venation yellowish brown.
Head in frontal view (Fig. 31), width 1.24× height; frons with dense reticulation; lower face flat, reticulation on lower face same as that on frons; eye height 0.7× head height, eyes separated by 1.09× eye height; antennal scrobe deep, extending upwards but not reaching anterior ocellus. Antennal insertion on lower ocular line, distance from upper margin of torulus to lower margin of anterior ocellus 2.35× distance from lower margin of torulus to clypeal margin; clypeus with longitudinal sculpture, only small area smooth; clypeal margin protruded, emarginate in middle with two sharp teeth; oral fossa width 0.46× head width. Head in lateral view, malar sulcus inconspicuous, eye height 3.3× malar space. Antennal scape 0.81× as long as eye height, not reaching lower margin of anterior ocellus; length of pedicel and flagellum combined shorter than head width (0.84×); pedicel in lateral view 2.6× as long as broad; anelli transverse; Fu 1 to Fu 4 slightly longer than broad respectively, Fu 5 and Fu 6 quadrate; each funicular segment with one row of longitudinal sensilla; clava slightly clavate, 2.43× as long as broad, micropilosity only limited to apex of third clava segment. Head in dorsal view 1.89× as wide as long; vertex convex, occipital carina strong; eye length 2× temple length; POL 1.64× OOL. Head 1.31× as broad as thorax. Mesosoma 1.38 × as long as broad. Pronotum with raised reticulation, pronotal collar slightly narrower than mesoscutum (0.86×); middle length of pronotum almost 1/9 as long as length of mesoscutum; collar not margined anteriorly, posterior margin of collar with a smooth band. Mesoscutum 1.86× as broad as long, with regular and dense reticulation; notauli incomplete and unconspicuous. Scutellum convex, 1.09× as broad as long, frenal line absent; reticulation same as on mesoscutum but slightly large on posterior part of scutellum. Propodeum (Fig. 32) medially ½ as long as scutellum; plica complete; median carina incomplete, occasionally with one or two short longitudinal ridge which interrupted in the middle; nucha short and smooth, separated with middle part of propodeum by a transverse shallow depression; spiracles elongate, 2× as long as broad, separated by the width of spiracles from hind margin of metanotum; area below spiracles with finely reticulation. Fore wing 2.25× as long as broad, without marginal fringe; basal vein with sparse setae, basal cell bare; speculum only stretched to 1/3 base of marginal vein; upper surface of costal cell bare, lower surface with a one complete row of setae and distal 1/3 with some scattered setae; submarginal vein 2.33× as long as marginal vein; marginal vein 1.67× as long as postmarginal vein; stigmal vein as long as postmarginal vein, slightly curved.
Male. Body length 2.1 mm; head and thorax blue-green; antenna light brownish except clava slightly dark, other segments yellow; legs yellow to yellowish brown except coxae concolorous with body; fore wing yellowish brown; gaster brown, with a yellow transverse bright ribbon at 1/3 base of gaster.

Dibrachys microgastri (Bouché, 1834) Figs 38-41
Diplolepis microgastri Bouché, 1834: 168; neotype female in ZMH by Peters andBaur 2011: 12. Syntypes presumed lost (Graham 1969: 811 Diagnosis. Body slender (Figs 38, 39), length 1.8-2.5 mm; gaster long ovate, spindleshaped. Head in frontal view (Fig. 40), width 1.21× height; antennal scrobe extending upwards but not reaching anterior ocellus; antennal insertion placed on lower ocular line; lower face at least slightly convex; sculpture on face larger than on vertex; clypeus with longitudinal striation; lower margin of clypeus slightly protruded, emarginated and with two blunt teeth. Antennal scape slightly shorter than eye height; not reaching lower margin of anterior ocellus; length of pedicle and flagellum shorter than head width; anelli transverse; each funicular segment quadrate except Fu 6 transverse; setae on antenna become an angle with antennal surface. Mesosoma 1.43× as long as broad; mid lobe of mesoscutum with coarse sculpture. Propodeum with complete plicae and weak median carina. Fore wing (Fig. 41)  Diagnosis. The new species belongs to Dibrachys s. str., and the mainly differences with Dibrachys microgastri (Bouché) are as follows: antenna of D. qinghaiensis sp. n. slender, each funicular segment at least slightly longer than its broad; antennal scape as long as eye height, and nearly reaching lower margin of anterior ocellus; but D. microgastri (Bouché) at least with several transverse funicular segment in distal of antenna, antennal scape distinctly shorter than eye height, and not reaching lower margin of anterior ocellus.
Description. Holotype. Female. Body (Figs 42, 43) length 2.2 mm. Head and mesosoma dark green, with brown gloss and metallic reflection; gaster dark brown. Antenna with scape and pedicel yellowish brown, but brownish in dorsum, other segments of antenna dark brown; mandible yellowish brown and margin of teeth brownish; legs yellowish brown except coxae concolorous with body; fore wing hyaline, wing venation light yellow.
Head in frontal view, 1.27× as wide as high (Fig. 45); frons with very dense reticulation; antennal scrobe with rather large reticulation; lower face flat, with densely transverse striation except lower edge of clypeus smooth; eye height 0.64× head height, eyes separated by 1.23× eye height; scrobe shallow, extending upwards but not reaching anterior ocellus. Antennal insertion slightly above lower ocular line, distance from upper margin of torulus to anterior ocellus 1.58× distance from lower margin of torulus to lower margin of clypeus; clypeal margin protruded, emarginate in middle with two small blunt teeth; oral fossa width 0.59× head width. Head in lateral view (Fig. 44) with malar sulcus inconspicuous, eye height 2.2× malar space. Antennal scape as long as eye height, nearly reaching lower margin of anterior ocellus; length of pedicel and flagellum combined shorter than head width (0.85×); pedicel in lateral view 3× as long as broad; anelli transverse; each funicular segment slightly longer than broad; each funicular segment with one row of longitudinal sensilla; clava slightly clavate, 2.57× as long as broad, micropilosity only limited to apex of third clava segment. Head in dorsal view 2× as wide as long, vertex convex, occipital carina strong; eye length 1.87× temple; POL 1.49× OOL.
Head width 1.31× as broad as thorax. Mesosoma 1.43× as long as broad. Pronotum with coarse reticulation, 0.87× as broad as thorax; pronotum with middle length 0.23× as long as mesoscutum, collar subhorizontal and not margined, posterior margin smooth. Mesoscutum 2× as broad as long, with finely dense reticulation (Fig. 46), posterior reticulation larger than anterior reticulation; notauli incomplete but conspicuous anteriorly. Scutellum flat, as long as broad, frenal line absent; finely reticulate. Propodeum medially 0.43× as long as scutellum, central area flat and with regular reticulation; plicae complete and parallel anteriorly, separated by 1.82× medial length of propodeum; median carina complete; propodeum with short, convex nucha; spiracles elongate, 2× as long as broad, separated by the width of spiracles from hind margin of metanotum; area below spiracles with conspicuous and deep reticulation. Fore wing (Fig. 47) 2.38× as long as broad, without marginal fringe; upper surface densely pubes-