Mesochorus (Stictopisthus) achterbergi, Riedel, 2023

Riedel, Matthias, 2023, Contribution to the taxonomy of the Southeast Asian Mesochorinae (Hymenoptera, Ichneumonidae), Zootaxa 5245 (1), pp. 1-72 : 7

Mesochorus (Stictopisthus) achterbergi nov. sp.

( Figs 1C , 8C , 14A )

Holotype. (♀) Malaysia: SE Sabah, nr Danum Valley Field C, c. 150 m, WONO, Mal. trap 10, 15–19.iii.1987, C. v. Achterberg, RMNH´87 (Leiden).

Description. ♀: Body length 3.5 mm. Fore wing 3.0 mm.

Head. Flagellum with 30 flagellomeres; 1 st flagellomere 5.9 × longer than wide and 1.6 × longer than 2 nd flagellomere, 0.7 × as long as eye; 2 nd flagellomere 3.6 × longer than wide; preapical flagellomere c 2.0 × longer than wide. Occipital carina shortly obsolete medially. Temple distinctly and roundly narrowed behind eye, dorsally c 0.4 × as long as eye. OED 1.6 × and OOD 0.7 × ocellar diameter. Frons almost smooth, with shallow triangular elevation below anterior ocellus and with two fine paramedian ridges between antennal sockets. Face ( Fig. 8C ) including facial orbit coarsely punctate, width 1.1 × combined length of face and clypeus and 1.1× eye length; inner eye margins slightly convergent ventrally. Subantennal transverse carina not dipped medially. Malar space with fine striae. Malar space 0.9 × 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. Side of pronotum largely smooth, with few very sparse punctures. Notaulus distinct in frontal 0.3 of mesoscutum. Mesoscutum with rather dense punctures, shining ( Fig. 14A ). Mesopleuron with coarse but sparse punctures, speculum smooth. Dorsal end of epicnemial carina separated from frontal margin of mesopleuron. Scuto-scutellar groove rather large, c 2.5 × wider than long, with c 6 longitudinal ridges ( Fig. 14A ). Scutellum rounded in profile, with fine sparse punctures, without lateral carina, not pointed apically. Area basalis trapezoid, about as long as wide.Area superomedia short, 1.5 × longer than wide and 0.8 × as long as area petiolaris, smooth; anterior transverse carina (costula) reaching its at 7/10 of its length. Area petiolaris longer than wide. Hind femur 3.1× longer than wide. Hind tarsus rather short; hind metatarsus 0.5 × as long as hind tibia and 2.7 × longer than 2 nd hind tarsomere; hind claw with 3 basal teeth, the distal tooth very long. Areolet shortly sessile frontally; vein 2m-cu slightly proximad its middle. Vein 1cu-a strongly postfurcal by 1.0 × its length. Postnervulus intercepted in its middle. Pterostigma 2.9 × longer than wide. Hind wing with 4 distal hamuli. Nervellus of hind wing vertical.

1 st tergite 2.5 × longer than wide. Postpetiolus with longitudinal rugae. 2 nd tergite 1.2 × wider than long. Thyridium comma-shaped. Ovipositor sheath with sparse setae, 7.1 × longer than wide, 0.5 × as long as hind tibia and 1.0 × as long as hind metatarsus, moderately bent upwards apically.

Color. Body mainly reddish-yellow. Flagellum ochreous basally, brownish distally. Palps, mandible except teeth, malar space, clypeus, face, ventral gena and ventral half of frontal orbit cream-yellow. Mesosoma reddishyellow; side of pronotum ventrally, hind edge of pronotum and tegula cream-yellow. 1 st tergite reddish-brown, basally yellowish. 2 nd tergite yellow, with brown triangular anterolateral spots. 3 rd tergite apically and 4 th tergite basally with roundish brown spot dorsally. Ovipositor sheath brown. Fore and mid coxae and trochanters creamyellow; legs otherwise reddish-yellow; hind tibia in apical 0.1 and hind tarsus entirely reddish-brown. Pterostigma hyaline, apical margin brownish.

♁ unknown.

Taxonomical remark. Within the subgenus Stictopisthus , this new species is characterized by the partly obsolete occipital carina, anterior transverse carina of propodeum reaching the area superomedia distally, rather wide face, and a long distal tooth of hind claw.

Figures

FIGURE 1. Oriental Mesochorinae, habitus from lateral. A−Orientochorus tonkinensis n. sp. HT, B−Astiphromma bicoloratus n. sp. HT, C−Mesochorus achterbergi n. sp. HT, D−M. annamensis n. sp. HT, E−M. brevipunctatus n. sp. HT, F−M. cariniscuta n. sp. HT.

FIGURE 8. Oriental Mesochorinae, face from frontal. A−Orientochorus tonkinensis n. sp. holotype (HT), B−Astiphromma bicoloratus n. sp. HT, C−Mesochorus achterbergi n. sp. HT, D−M. annamensis n. sp. HT, E−M. brevipunctatus n. sp. HT, F−M. cariniscuta n. sp. HT, G−M. controversus n. sp. HT, H−M. diversidens n. sp. HT (♀).

FIGURE 14. Oriental Mesochorinae, mesoscutum from dorsal.A−Mesochorus achterbergi n. sp. HT (♁), B−M. carinisctua n. sp. HT with carinate scutellum, C−M. flavopronotalis n. sp. HT, D−M. kinabaluensis n. sp. HT, E−M. sabahensis n. sp., F−M. malucutus n. sp. HT.