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

description: Mesochorus (Mesochorus) pictiloides nov. sp.
(Figs 5B, 11E, 18H, 23H)
Holotype (♀) Malaysia: SE Sabah, nr Danum Valley Field C, WO, Malaise trap 11, c. 150 m, 20–26.iii.1987, C. v. Achterberg, RMNH´87 (Leiden).
Paratype. (♀) Indonesia: Sula Isl., Mangole, near Buya, Mal. trap 15, c 445 m, 13.x. –2.xi.1993, C.v.Achterberg, RMNH´93 (Leiden).
Etymology. The name refers to the resemblance with the Palaearctic Mesochorus pictilis Holmgren.
Description. ♀: Body length 4.3 mm (3.5 mm in paratype). Fore wing 3.1–3.2 mm.
Head. Flagellum with 26–28 flagellomeres; 1 st flagellomere 6.1–6.7 × longer than wide and 1.4× longer than 2 nd flagellomere, 0.6 × as long as eye; 2 nd flagellomere 4.0–4.3 × longer than wide; preapical flagellomere 2.6–3.0 × longer than wide. Occipital carina widely absent medially. Temple distinctly and roundly narrowed behind eye, dorsally c 0.3 × as long as eye. OED 1.6–1.7 × and OOD 0.4–0.6 × ocellar diameter. Vertex with few very sparse punctures, smooth. Frons smooth medially, with sparse punctures laterally. Face (Fig. 11E) coarsely punctate, width 1.0 × combined length of face and clypeus and 1.0 × eye length; inner eye margins parallel ventrally. Subantennal transverse carina slightly dipped medially. Malar space, mandible and ventral half of facial orbit widely striate. Malar space 0.9 × as long as width of mandibular base. Mandible with two teeth, ventral tooth as long as dorsal tooth or slightly longer. Genal carina reaching hypostomal carina away from mandibular base, both carinae low.
Mesosoma. 1.6 × longer than high. Mesoscutum densely punctate, shining. Mesopleuron and metapleuron with coarse and dense punctures, speculum smooth. Dorsal end of epicnemial carina separated from frontal margin of mesopleuron. Juxtacoxal carina absent. Scuto-scutellar groove c 2.0 × wider than long, smooth with fine punctures. Scutellum rounded in profile, with rather dense coarse punctures. Propodeum (Fig. 18H) completely carinate. Area basalis triangular, about as long as wide. Area superomedia pentagonal, 1.4 × (1.6 × in paratype) longer than wide and 0.6 × (0.8 × in paratype) as long as area petiolaris, smooth; anterior transverse carina (costula) reaching 5/10– 6/10 of its length.Area petiolaris large, 1.8 × (1.3 × in paratype) longer than wide. Hind femur 4.0–4.6 × longer than wide; hind metatarsus 0.6 × as long as hind tibia and 2.8 × longer than 2 nd hind tarsomere; hind claw with two basal teeth. Areolet shortly sessile frontally; vein 2m-cu proximad its middle. Vein 1cu-a postfurcal by 0.4 × its length. Postnervulus intercepted basad its middle. Pterostigma 3.3× longer than wide. Hind wing with 4 distal hamuli. Nervellus of hind wing vertical.
Metasoma. 1 st tergite 2.6 × longer than wide. Postpetiolus with some longitudinal rugae in apical half. 2 nd tergite 1.1 × wider than long. Thyridium comma-shaped. Ovipositor sheath (Fig. 23H) stick-shaped, with sparse setae, 11.5–11.7 × longer than wide, 0.6 × as long as hind tibia and 1.0 × (1.2 × in paratype) as long as hind metatarsus.
Color. Body mainly reddish-yellow. Scape and pedicel yellow; flagellum brownish. Palps, mandible except teeth, malar space, wide facial orbit, and ventral half of frontal orbit cream-yellow. Mesosoma reddish-yellow; pronotum ventrally, hind edge of pronotum and tegula cream-yellow. 1 st tergite reddish-yellow, postpetiolus with lateral brown stripes. 2 nd tergite yellow, with large blackish V-shaped basal spot. 3 rd tergite brown, with halfmoonshaped yellow spot in basal half. Following tergites yellow; 4 th to 6 th tergites with roundish brown basal spots. Ovipositor sheath brown. Fore and mid coxae and femora, and all trochanters cream-yellow. Legs otherwise yellowish; hind tibia in basal 0.1 and apical 0.2 blackish (entirely yellow in paratype); hind tarsus mainly brownish. Pterostigma 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 wide face, widely striate facial orbit, punctate scuto-scutellar groove and long area petiolaris.
The paratype from the Moluccas differs from the Malaysian holotype by entirely yellow hind tibia, longer area superomedia and longer ovipositor. It is possible that this specimen represents a closely related but separate species.
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 27-28, DOI: 10.11646/zootaxa.5245.1.1, http://zenodo.org/record/7673309