Mesochorus (Mesochorus) malaysiacus, Riedel, 2023

Riedel, Matthias, 2023, Contribution to the taxonomy of the Southeast Asian Mesochorinae (Hymenoptera, Ichneumonidae), Zootaxa 5245 (1), pp. 1-72 : 21-22

Mesochorus (Mesochorus) malaysiacus nov. sp.

( Figs 4A , 10F , 18D , 23B )

Holotype. (♀) Malaysia: SE Sabah, nr Danum Valley Field C, c. 150 m, WONO, Mal. trap 5, 26.v. –20.vi.1987, RMNH´87, C. v. Achterberg & D. Kennedy (Leiden).

Description. ♀: Body length 3.7 mm. Fore wing 3.5 mm.

Head. Flagellum with 25 flagellomeres; 1 st flagellomere 6.1 × longer than wide and 1.5 × longer than 2 nd flagellomere, 0.6 × as long as eye; 2 nd flagellomere 3.9 × longer than wide; preapical flagellomere 2.8 × longer than wide. Temple strongly and roundly narrowed behind eye, dorsally c 0.3 × as long as eye. OED 1.6 × and OOD 0.5 × ocellar diameter. Occipital carina complete medially. Frons almost smooth medially, with few punctures and fine transverse striation laterally. Face ( Fig. 10F ) densely punctate, without central longitudinal ridge dorsally, width 1.0 × combined length of face and clypeus and 1.0 × eye length; inner eye margins parallel. Subantennal transverse carina dipped medially. Malar space and facial orbit widely and coarsely striate. Malar space 1.0 × as long as width of mandibular base. Mandible with two equal teeth. Genal carina reaching hypostomal carina away from mandibular base, both carinae low.

Mesosoma . 1.6 × longer than high, covered with whitish setae. Mesoscutum densely punctate, partly rugosepunctate postero-medially. Scuto-scutellar groove smooth. Scutellum moderately convex, without lateral carina, not pointed apically. Mesopleuron with rather dense punctures fronto-dorsally and with coarse but sparse punctures ventrally. Dorsal end of epicnemial carina separated from frontal margin of mesopleuron. Metapleuron with fine sparse punctures. Submetapleural carina low. Propodeum ( Fig. 18D ) completely carinate. Area basalis trapezoid, shortly longer than wide. Area superomedia 1.9 × longer than wide and 1.0 × as long as area petiolaris; anterior transverse carina (costula) reaching at 4/10 of its length. Area petiolaris 1.4 × longer than wide. Hind femur 4.3 × longer than wide; hind metatarsus long, 0.5 × as long as hind tibia and 2.8 × longer than 2 nd hind tarsomere; hind claw with 2 short basal teeth. Areolet shortly sessile frontally; vein 2m-cu in its middle. Vein 1cu-a postfurcal by 0.5 × its length. Postnervulus intercepted basad its middle. Pterostigma 3.3 × longer than wide. Hind wing with 5 distal hamuli. Nervellus of hind wing slightly reclivous.

Metasoma. 1 st tergite rather stout, 2.2 × longer than wide. Postpetiolus smooth, with few rugae. 2 nd tergite 1.2 × wider than long. Thyridium comma-shaped. Ovipositor sheath ( Fig. 23B ) with sparse setae, stick-shaped, 11.2 × longer than wide, 0.6 × as long as hind tibia and 1.1 × as long as hind metatarsus.

Color. Head reddish-yellow; palps, mandible except teeth, malar space and facial orbit pale yellow; stemmaticum blackish. Flagellum brownish; basal flagellomeres ochreous; scape and pedicel yellowish. Mesosoma reddishyellow; hind edge of pronotum and tegula cream-yellow. 1 st tergite reddish, yellow basally; postpetiolus with brownish stripes laterally. 2 nd tergite brown, with large yellowish spot with curved frontal margin in apical 2/3. 3 rd tergite brown; following tergites yellowish, dorsally ± with brownish spots. Ovipositor sheath pale brown. Fore and mid legs yellow; hind leg entirely reddish-yellow; hind tibia not infuscate. Pterostigma ochreous-hyaline.

♁ unknown.

Taxonomical remark. This new species belongs to the pectoralis group sensu Schwenke (1999), e. g. basal tergites black, mid tergites with pale color pattern, apical tergite ± darkened. It is characterized by: widely striate facial orbit, entirely yellowish mesosoma and hind tibia, and long and stick-shaped ovipositor sheath.

Figures

FIGURE 4. Oriental Mesochorinae, habitus from lateral. A−Mesochorus malaysiacus n. sp. HT, B−M. malucutus n. sp. HT, C−M. nigripleuris n. sp., D−M. nigrofemur n. sp. HT (♀), E−M. nigrofemur n. sp. PT (♁), F−M. nigromaculatus n. sp. HT.

FIGURE 10. Oriental Mesochorinae, face from frontal. A− Mesochorus lamdongensis n. sp. HT, B−M. longimurus n. sp. HT, C−M. longistylus n. sp. HT, D−M. longistylus n.sp. (frons from dorsal), E−M. longivalvator n. sp. HT, F−M. malaysiacus n. sp. HT, G−M. malucutus n. sp. HT, J−M. nigripleuris n. sp. HT.

FIGURE 18. Oriental Mesochorinae, propodeum from dorsal. A− Mesochorus kinabaluensis n. sp. HT, B−M. longimurus n. sp. HT, C−M. longistylus n. sp. HT, D−M. malaysiacus n. sp. HT, E−M. malucutus n. sp. HT, F−M. nigripleuris n. sp., G−M. nigromaculatus n. sp. HT, H−M. pictiloides n. sp. HT, I−M. pterostigmator n. sp.

FIGURE 23. Oriental Mesochorinae, ovipositor sheath from lateral.A−Mesochorus longivalvator n. sp. HT, B−M. malaysiacus n. sp. HT, C−M. malucutus n. sp. HT, D−M. nigripleuris n. sp., E−M. nigrofemur n. sp. HT (♀), F−M. nigromaculatus n. sp. HT, G−M. paratenebris n. sp. HT, H−M. pictiloides n. sp. HT, I−M. pterostigmator n. sp., J−M. rufator n. sp. HT, K−M. sabahensis n. sp. HT, L−M. sapaensis n. sp. HT, M−M. semifuscus n. sp. HT, N−M. semipunctatus n. sp. HT.