Mesochorus (Stictopisthus) achterbergi Riedel 2023, nov. sp.

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.