Mastrus nigrus Sheng & Zeng

Sheng, Mao-Ling & Zeng, Xiang-Fu, 2010, Species of the genus Mastrus Foerster (Hymenoptera, Ichneumonidae) of China with descriptions of two new species parasitizing sawflies (Hymenoptera), ZooKeys 57, pp. 63-73 : 64-67

Mastrus nigrus Sheng & Zeng sp. n. Figs 1, 2, 3, 4, 5, 6

Etymology.

The specific name is derived from the body being entirely black.

Types.

Holotype, female, CHINA: Shennongjia, 2360m, Hubei Province, 15 April 2009, leg. MAN-QUN WANG. Paratypes: 2 females and 1 male, CHINA: Shennongjia, 2110 to 2360m, Hubei Province, 15 to 20 April 2009, MAN-QUN WANG.

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 profile of scape with distinct punctures. Tegulae black.

Description.

Female. Body length 5.5-7.0 mm. Fore wing length 5.0-6.0 mm. Ovipositor sheath length 2.5-2.8 mm.

Head. Face (Figure 2) 1.9-2.1 times as wide as long, with fine 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. Subocular sulcus indistinct. Gena with fine leathery texture and unclear punctures, about as long as middle width of compound eye. Vertex (Figure 3) with fine, unclear punctures, posterior portion with indistinct oblique lines. Postocellar line about 0.7 times as long as ocular-ocellar line. Upper portion of frons approximately flat, with texture as that of face; lower portion concave and shiny, with fine, transverse wrinkles. Antenna short, with 27 to 28 flagellomeres, apical portion not attenuated, ratio of length from first to fifth flagellomeres: 6.0:6.0:5.3:4.1:3.3. First and second flagellomeres about 3.75 times as long as widest diameter; ventral profile of scape with distinct punctures. Occipital carina complete.

Mesosoma. Pronotum smooth, upper half of anterior margin with weak longitudinal wrinkles and punctures; median portion with dense oblique transverse wrinkles; upper posterior portion with weak, dense, oblique longitudinal wrinkles. Epomia weak. Mesoscutum evenly convex, with fine granulose texture, punctures indistinct. Notaulus evident on front portion of mesoscutum. Scutoscutellar groove smooth, with weak longitudinal wrinkles. Scutellum evenly convex, with fine granulose texture and fine punctures, diameter of puncture 1.0 to 2.0 times as long as distance between punctures. Postscutellum short, with fine punctures. Mesopleuron (Figure 4) with dense and strong transverse wrinkles, upper anterior corner with weak and short oblique wrinkles. Epicnemium with fine punctures, diameter of puncture approximately as long as distance between punctures. Epicnemial carina strong, upper end reaching to subalar prominence. Speculum small, with weak and fine transverse lines. Sternaulus sharp, reaching to hind margin of mesopleuron. Metapleuron rough, anterior portion with unclear transverse wrinkles, hind portion with unclear longitudinal wrinkles. Anterior section of juxtacoxal carina distinct, hind section unclear. Submetapleural carina complete and strong. Wings 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 3.5 times as long as cu-a. Legs robust. Ratios of length of hind tarsomeres 1:2:3:4:5 are 10.0:4.0:3.0:1.7:2.0. Propodeum (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 fine 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 fine 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 fine granulose texture, posterior portion with indistinct, fine, longitudinal wrinkles. Median dorsal carinae indistinct. Dorsolateral and ventrolateral carinae complete. Spiracle circular, very small, located slightly behind middle of first tergum. Second tergum approximately 0.7 times as long as apical width, with texture as that of mesoscutum. Third tergum 0.6 times as long as basal width, with fine 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 profile of apical portion of flagellomeres 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 profiles), 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 flagellomeres, tenth and eleventh flagellomeres with linear tyloids. Ventral profile 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.

The mature larva forms a cocoon outside the body of the larval host and inside the cocoon of the host.

Remarks.

This 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 profile 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 profile of scape almost smooth, punctures indistinct; costula connecting area superomedia at its middle; tegulae, apical portion of femora, tibiae and tarsi red.