Mesochorus (Mesochorus) tenebris, Riedel, 2023

Riedel, Matthias, 2023, Contribution to the taxonomy of the Southeast Asian Mesochorinae (Hymenoptera, Ichneumonidae), Zootaxa 5245 (1), pp. 1-72 : 40-41

Mesochorus (Mesochorus) tenebris nov. sp.

( Figs 7C , 13E , 20A, 24G)

Holotype. (♀) NW Vietnam: Tonkin, Hoang Lien N. R., 10 km SW Sa Pa , c. 1550 m, 22–29.x.1999, Malaise traps, C. v. Achterberg, RMNH´99 (Leiden).

Paratypes. (♀) similar label (coll. Riedel); (♀) N Vietnam: Thùa Thién-Hué, Bach Ma N.P., 490 m, N 16°13´44´´ E 107°51´13´´, 28.iii.–12.iv.2011, Mal. tr. 30, C. v. Achterberg, RMNH´11 (Leiden) .

Etymology. The species name refers to the mainly dark body color (“tenebris” is the Latin term for “dark”).

Description. ♀: Body length 3.0– 3.5 mm. Length of fore wing 3.1 mm.

Head. Flagellum with 24–27 flagellomeres; 1 st flagellomere 8.1–8.7 × longer than wide and 1.6 × longer than 2 nd flagellomere, 0.8–0.9 × as long as eye; 2 nd flagellomere 5.0–5.4 × longer than wide; preapical flagellomere 1.9– 2.3 × longer than wide. Temple moderately and roundly narrowed behind eye, dorsally c 0.7 × as long as eye. OED 1.7–2.0 × and OOD 0.9–1.1 × ocellar diameter. Occipital carina complete medially. Frons densely punctate dorsally. Face ( Fig. 13E ) punctate, with superficial punctures centrally and weak central longitudinal ridge medially, 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 ventral 0.4 of facial orbit widely 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 . 1.7 × longer than high. Mesoscutum densely punctate (in one paratype rugose-punctate) posteromedially, densely but superficially punctate on lateral lobe. Scuto-scutellar groove smooth. Scutellum moderately convex, finely punctate, without lateral carina, not pointed apically. Mesopleuron with rather dense punctures frontodorsally and very sparse fine punctures ventrally. Dorsal end of epicnemial carina separated from frontal margin of mesopleuron. Metapleuron with fine sparse punctures. Juxtacoxal carina absent. Submetapleural carina low. Propodeum ( Fig. 20A ) completely carinate. Area basalis triangular, slightly longer than wide. Area superomedia 1.6 × longer than wide and 1.1 × longer than area petiolaris; anterior transverse carina (costula) reaching its middle. Area petiolaris 1.1 × longer than wide. Hind femur 4.6–5.6 × longer than wide; hind metatarsus 0.5 × as long as hind tibia and 2.7 × longer than 2 nd hind tarsomere; hind claw with one or two visible basal teeth. Areolet shortly sessile frontally; vein 2m-cu proximad or in its middle. Vein 1cu-a slightly postfurcal by 0.2× its length. Postnervulus intercepted basad its middle. Pterostigma 3.3–3.4× longer than wide. Hind wing with 4 distal hamuli. Nervellus of hind wing vertical.

Metasoma. 1 st tergite 2.6–3.0 × longer than wide. Postpetiolus smooth, with few fine punctures, in one paratype with weak central impression. 2 nd tergite 1.1–1.4 × wider than long. Thyridium comma-shaped. Ovipositor sheath ( Fig. 24G ) densely pilose basally, sparsely pilose in apical 2/3, 10.1 × longer than wide, 0.6 × as long as hind tibia and 1.1 × longer than hind metatarsus, slightly narrowed in apical 0.3.

Color. Scape and flagellum brown, pedicel ochreous. Face, clypeus, frontal, vertical and outer orbits reddishyellow. Palps, mandible except teeth, malar space, facial orbit and ventral gena cream-yellow. Frons medially, stemmaticum and occiput largely brown. Ventral and upper margins of pronotum ± yellowish; hind edge of pronotum and tegula cream-yellow; mesosoma otherwise blackish. 1 st tergite black, pale yellow basally. 2 nd tergite black, with pale yellow band in apical 0.2. 3 rd tergite black, with pale yellow band or triangular spot in basal 0.1–0.2. Following tergites black. 3 rd to 6 th sternites with lateral brownish spots. Ovipositor sheath brown. Fore and mid coxae and all trochanters cream-yellow; fore and mid legs otherwise pale yellow. Hind coxa yellow ventrally, brown dorsally. Hind femur reddish-yellow, with ± distinct brownish stripe externally; hind tibia cream-yellow, brown basally and in apical 0.3, and with subbasal brownish spot. Hind tarsus pale brownish. Pterostigma whitish-hyaline (in one paratype pale brownish).

♁ unknown.

Taxonomical remark. With its sessile areolet, postfurcal vein 1cu-a, stick-shaped ovipositor and short area superomedia, this species belongs to the dispar group sensu Schwenke (1999). It is characterized by the mainly black and typical color pattern of metasoma, mainly black mesosoma with yellowish pronotum, whitish pterostigma, and dorsally brown hind coxa.

Figures

FIGURE 7. Oriental Mesochorinae, habitus from lateral.A−Mesochorus sumaterae n. sp. HT, B−M. templator n. sp. HT, C−M. tenebris n. sp., D−M. tonkinensis n. sp. HT, E−M. trani n. sp. HT, F−M. vietnamensis n. sp. HT.

FIGURE 13. Oriental Mesochorinae, face from frontal. A−Mesochorus sulaensis n. sp. HT (♁), B−M. sulaensis n. sp. PT (m#), C−M. sumaterae n. sp. HT, D−M. templator n. sp. HT, E−M. tenebris n. sp., F−M. tonkinensis n. sp. HT, G−M. trani n. sp. HT, H−M. vietnamensis n. sp. HT.

FIGURE 20. Oriental Mesochorinae, propodeum from dorsal. A−Mesochorus tenebris n. sp. HT, B−M. tonkinensis n. sp. HT, C−M. trani n. sp. HT, D−M. vietnamensis n. sp. HT.

FIGURE 24. Oriental Mesochorinae, ovipositor sheath from lateral. A−Mesochorus siamensis n. sp., B−M. stigmaticolor n. sp. HT, C−M. striatofacies n. sp. HT, D−M. sulaensis n. sp. HT, E−M. sumaterae n. sp. HT, F−M. templator n. sp. HT, G−M. tenebris n. sp., H−M.