Species of the genus Mastrus Förster (Hymenoptera, Ichneumonidae) of China with descriptions of two new species parasitizing sawflies (Hymenoptera)

Abstract Four species of Mastrus Förster, 1869 are reported from China. Two, Mastrus nigrus Sheng & Zeng, sp. n. reared from Arge pullata (Zaddach) and Mastrus rugotergalis Sheng & Zeng, sp. n. reared from Diprion jingyuanensis Xiao & Zhang, are new to science. One, Mastrus deminuens (Hartig, 1838), is a parasitoid of Pachynematus itoi Okutani. A key to species of Mastrus Förster known in China is provided.


Introduction
Mastrus Förster, 1869, belonging to the subfamily Cryptinae of Ichneumonidae (Hymenoptera), comprises 50 described species (Yu et al. 2005), of which 30 are known from the Palearctic, 16 from the Nearctic, one is Holarctic, one from the Neotropics, and two from the Oriental Region. Th e European species of the pictipes group of Mastrus were revised by Horstmann (1990).

Methods
Materials used were collected using the following methods.
Rearing parasitoids. Cocoons of sawfl ies were collected from forests where there had been an outbreak of sawfl y larvae lasting two or three years. Cocoons were stored individually in glass tubes with a piece of fi lter paper dipped in distilled water for maintaining moisture and plugged tightly with absorbent cotton at room temperature. Glass tubes are 60 mm long and 6 mm diameter. Emerged insects were collected daily.
Some European specimens of M. deminuens (Hartig, 1838) for comparing with Chinese specimens mentioned in this article were provided by Dr. G. Broad and Dr. K. Horstmann. Photographs of the type of Mastrus ineditus were taken by Dr. A. Khalaim.
Th e morphological terminology mostly follows Townes (1969). Wing vein nomenclature is based upon Ross (1936) and the terminology of Mason (1986Mason ( , 1990 Diagnosis. Clypeal suture weak and indistinct; subapex of clypeus slightly raised. Hind wing vein 1-cu strongly inclivous, about 3.5 times as long as cu-a. Area superomedia of propodeum approximately as wide as long. Ventral profi le of scape with distinct punctures. Tegulae black.
Head. Face (Figure 2) 1.9-2.1 times as wide as long, with fi ne granulose texture and dense punctures, diameter of punctures 1.0-2.0 times distance between punctures, weakly convex centrally; upper margin medially concave. Clypeal suture weak and indistinct. Clypeus slightly convex, 2.5 times as wide as long; basal portion with texture as that of face, but medially sparsely punctate and apically smooth; subapex somewhat raised; apical margin with two small median protruberances. Mandible with dense punctures, upper tooth slightly longer than lower tooth. Median portion of cheek slightly rough, hind portion with punctures. Malar space approximately as long as basal width of mandible.  posterior portion with weak, dense, oblique longitudinal wrinkles. Epomia weak. Mesoscutum evenly convex, with fi ne granulose texture, punctures indistinct. Notaulus evident on front portion of mesoscutum. Scutoscutellar groove smooth, with weak longitudinal wrinkles. Scutellum evenly convex, with fi ne granulose texture and fi ne punctures, diameter of puncture 1.0 to 2.0 times as long as distance between punctures. Postscutellum short, with fi ne punctures. Mesopleuron (Figure 4) Figure 5) completely areolate, carinae strong. Area basalis an inverse trapezium, with weak longitudinal wrinkles. Area superomedia hexagonal, approximately as wide as long, with very weak and fi ne transverse wrinkles. Costula connecting area superomedia distinctly behind its middle. Area petiolaris strongly sloping, with dense, oblique, transverse wrinkles. Area externa slightly coriaceous. Area dentipara, areae spiracularis and lateralis with irregular fi ne wrinkles. Area posteroexterna with strong longitudinal wrinkles. Spiracle circular, very small. Propodeal apophysis short and compressed. Metasoma. First tergum 1.8 times as long as apical width, with fi ne granulose texture, posterior portion with indistinct, fi ne, longitudinal wrinkles. Median dorsal carinae indistinct. Dorsolateral and ventrolateral carinae complete. Spiracle circular, very small, located slightly behind middle of fi rst tergum. Second tergum approximately 0.7 times as long as apical width, with texture as that of mesoscutum. Th ird tergum 0.6 times as long as basal width, with fi ne granulose texture. Fourth and following terga strongly convergent backward. Ovipositor sheath 1.1 to 1.2 times as long as hind tibia. Ovipositor slightly compressed. Apical portion of lower valve with 7 weak ridges, basal 3 widely spaced, distal 4 moderately close together.
Color (Figure 1). Black, except the following. Apical margin of pedicel yellowish brown. Ventral profi le of apical portion of fl agellomeres dark brown. Upper margin of mandible slightly reddish brown. Maxillary and labial palpi brownish black. Ends of front and middle trochanters, basal ends of all femora, apical portions of front and middle femora, front tibiae (at least ventral profi les), brown; middle tibiae blackish brown. Tarsi more or less brown. Posterior portion of sixth and seventh terga white. Stigma brownish black except white base. Veins blackish brown.
Male. Body length about 6.0 mm. Fore wing length about 4.8 mm. Antenna with 23 fl agellomeres, tenth and eleventh fl agellomeres with linear tyloids. Ventral profi le of scape, mandibles except teeth, maxillary and labial palpi, upper posterior corner of pronotum, tegulae, coxae and trochanters of front and middle legs buff . Front and middle legs sandy beige, except apices of tarsi slightly darkened. Hind femora and basal 0.7 of tibiae reddish brown, apical portion of each tarsal segment slightly brown.
Host. Arge pullata (Zaddach) (Hymenoptera: Argidae). Host plant. Betula albo-sinensis Burkill (Betulaceae). Biology. Th e mature larva forms a cocoon outside the body of the larval host and inside the cocoon of the host.
Remarks. Th is new species is similar to Mastrus ineditus but can be distinguished from the latter by the following combination of characters: clypeal suture weak and indistinct; subapex of clypeus slightly raised; ventral profi le of scape with distinct punctures; costula connecting area superomedia distinctly behind its middle; tegulae black; middle and hind femora, tibiae and tarsi black or mostly black. Mastrus ineditus: clypeal suture distinct and deep; apical portion of clypeus depressed and lamelliform; ventral profi le of scape almost smooth, punctures indistinct; costula connecting area superomedia at its middle; tegulae, apical portion of femora, tibiae and tarsi red. (Kokujev, 1909) Figs 7, 8, 9 Notes. No specimens were examined. Figures of the type, including the body (lateral profi le), face, mesopleuron, wings, propodeum and ovipositor, were checked. Drafted fi gures by Dr. K. Horstmann were consulted.
Head. Face (Fig. 11) 1.9-2.0 times as wide as long, with granulose texture and indistinct fi ne punctures, diameter of punctures 0.5-2.0 times distance between punctures, evenly convex centrally; upper margin with a small median protuberance. Clypeal suture weak and unclear. Clypeus slightly convex, 2.2 times as wide as long; basal portion with indistinct fi ne punctures, apically smooth and sparsely punctate; apical margin with two small median protruberances. Mandible with indistinct sparse punctures, upper tooth distinctly longer than lower tooth. Cheek fi nely granulated. Malar  (Kokujev, 1909). 7 Face 8 Wings 9 Apical portion of ovipositor. Mesosoma. Anterior portion of pronotum smooth, upper portion with punctures; median portion with dense oblique transverse wrinkles; upper posterior portion with fi ne granulose texture, punctures distinct. Epomia weak. Mesoscutum with fi ne granulose texture, punctures indistinct. Notaulus evident on front portion of mesoscutum. Scutoscutellar groove nearly smooth, with weak longitudinal wrinkles. Scutellum shiny, evenly convex, with fi ne punctures, diameter of puncture 1.0 to 3.5 times as long as distance between punctures. Postscutellum transverse, anterolaterally deeply concave, punctures indistinct. Mesopleuron with dense and oblique transverse wrinkles, upper anterior corner with weak and short transverse wrinkles. Epicnemium with fi ne punctures, diameter of puncture approximately as long as distance between punctures. Epicnemium punctate indistinctly. Epicnemial carina strong, upper end reaching to subalar prominence. Speculum small, anterior portion with weak and fi ne transverse lines. Sternaulus sharp, reaching to hind margin of mesopleuron. Metapleuron slightly rough, with unclear oblique transverse wrinkles. Juxtacoxal carina anteriorly distinct, hind section unclear. Juxtacoxal and submetapleural carinae complete and strong. Wings brownish hyaline. Fore wing with vein 1cu-a distal of 1/M by about 0.3 times length of 1 cu-a. Vein 3rs-m absent; 2rs-m about 1.1 to 1.3 times as long as distance between it 2rs-m and 2m-cu. Vein 2-Cu approximately 2.0 times as long as 2cu-a. Hind wing vein 1-cu strongly inclivous, about 4.0 times as long as cu-a. Legs robust. Ratios of length of hind tarsomeres 1:2:3:4:5 are 10.0:4.2:3.0:1.7:3.0. Propodeum completely areolate, carinae strong. Area basalis inverse trapezium, almost smooth. Area superomedia hexagonal, 1.3 to 1.7 times as wide as long, slightly coriaceous. Costula connecting area superomedia at its apical 0.3. Area petiolaris strongly sloping, centrally rough, with short oblique wrinkles. Area dentipara with irregular fi ne wrinkles. Area posteroexterna with strong irregular wrinkles. Areae spiracularis and lateralis with irregular transverse wrinkles. Spiracle circular, very small, close to lateral longitudinal carina. Propodeal apophysis short and compressed.
Metasoma. First tergum 1.4 to 1.6 times as long as apical width. Petiole with granulose texture. Postpetiole with fi ne, longitudinal wrinkles. Without median dorsal carinae. Dorsolateral and ventrolateral carinae complete. Spiracle circular, very small, slightly convex, located at apical 0.4 of fi rst tergum. Second tergum (Fig. 12) approximately 0.6 times as long as apical width, with more or less distinct longitudinal wrinkles. Th ird tergum 0.6 times as long as basal width, 0.7 times as long as apical width, almost smooth. Fourth and following terga strongly convergent backward. Ovipositor sheath 1.1 to 1.2 times as long as hind tibia. Ovipositor not compressed, with weak nodus. Apical portion of lower valve with weak oblique ridges, basal 2 widely spaced.
Color (Fig. 10). Black, except the following. Ventral profi les of scape and pedicel, fl agellomeres 1 to 4 (5), legs except hind tibiae and tarsi slightly darkish brown, brown. Mandible yellowish brown, except teeth black. Maxillary and labial palpi dust-coloured. Longitudinal fl eck of median portion of petiole, postpetiole, second and third terga, basal median portion of fourth tergum red. Tegulae darkish brown. Posterior margins of sixth and seventh terga and most of eighth tergum white. Stigma, except white base and veins, blackish brown.
Male. Body length about 5.0 mm. Fore wing length about 4.0 mm. Face with distinct punctures. Antenna with 21 fl agellomeres, tenth and eleventh fl agellomeres with linear tyloids. Ventral profi les of scape and pedicel whitish yellow. Tegulae buff . Middle and hind coxae blackish brown. Second and third terga brown with more or less irregular darkish fl eck.
Remarks. Th is new species is similar to Mastrus deminuens but can be distinguished from the latter by the following combination of characters: face distinctly and densely punctate on a slightly granulate background; second tergum with more or less distinct longitudinal wrinkles, or fi nely granulose basally-centrally. Mastrus deminuens: face granulate and dull, with fi ne punctures; second tergum distinctly granulate and dull, or partly and obliquely granulate-strigose.