Mesochorus (Mesochorus) malaysiacus Riedel 2023, nov. sp.
Creators: name: Riedel, Matthias
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Ichneumonidae
Mesochorus
Mesochorus malaysiacus

description: 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.
description: Published as part of Riedel, Matthias, 2023, Contribution to the taxonomy of the Southeast Asian Mesochorinae (Hymenoptera, Ichneumonidae), pp. 1-72 in Zootaxa 5245 (1) on pages 21-22, DOI: 10.11646/zootaxa.5245.1.1, http://zenodo.org/record/7673309