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

description: Mesochorus (Mesochorus) semifuscus nov. sp.
(Figs 6A, 12B, 12C, 19D, 23M, 25)
Holotype. (♀) NW Vietnam: Tonkin, Hoang Lien N. R., 15 km W Sa Pa, c. 1900 m, 15–21.x.1999, Malaise traps, C. v. Achterberg, RMNH´99 (Leiden).
Paratypes: (♁) similar label (Leiden); (♀) N Vietnam: Viet Try, nr Thanh Son, Thuong Cuu 20°59´N 105°8´E, 350–400 m, 11–16.x.1999, Malaise traps, R. de Vries, RNMH´99 (coll. Riedel); (♁) NW Vietnam: Tonkin, Hoang Lien N. R., 10 km SW Sa Pa, c. 1550 m, 22–29.x.1999, C. v. Achterberg, RMNH´99 (Leiden); (2 ♀♀) N Vietnam: Thùa Thién-Hué, Bach Ma N.P., 105 m, N 16°14´46´´ E 107°52´06´´, 27.iii. –12.iv.2011, Mal. tr. 19, C. v. Achterberg, RMNH´11 (Leiden and coll. Riedel); (♁) S Vietnam: Lam Dong, Bidoup Nuiba N.P., nr. Da Lat, Mal. trap 1–12, 1650–1700 m, 11–19.x.2005, C. v. Achterberg & R. de Vries, RMNH´05 (Leiden).
Etymology. The species name refers to the partly blackish color pattern.
Description. ♀: Body length 5.1–5.5 mm. Length of fore wing 4.2–4.9 mm.
Head. Flagellum with 36-38 flagellomeres; 1 st flagellomere 7.9 × longer than wide and 2.0 × longer than 2 nd flagellomere, 0.8 × as long as eye; 2 nd flagellomere 4.3 × longer than wide; preapical flagellomere 2.5 × longer than wide. Temple strongly and roundly narrowed behind eye, dorsally c 0.3 × as long as eye. OED 1.4 × and OOD 0.5 × ocellar diameter. Occipital carina complete medially. Frons with fine sparse punctures and fine lateral aciculation. Face (Fig. 12B) coarsely punctate, with strong central longitudinal ridge, 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 0.5 of facial orbit widely striate. Malar space 0.5–0.6 × as long as width of mandibular base. Mandible with two teeth, ventral tooth longer than dorsal tooth. Genal carina reaching hypostomal carina away from mandibular base, both carinae low.
Mesosoma. 1.6 × longer than high. Mesoscutum densely punctate. Scuto-scutellar groove smooth. Scutellum moderately convex, finely punctate, without lateral carina, not pointed apically. Mesopleuron with dense punctures fronto-dorsally and sparse punctures ventrally. Dorsal end of epicnemial carina separated from frontal margin of mesopleuron. Metapleuron with fine sparse punctures. Submetapleural carina slightly lamelliform. Propodeum (Fig 19D) completely carinate. Area basalis triangular, with short apical stalk. Area superomedia 1.5 × longer than wide and 0.7 × as long as area petiolaris; anterior transverse carina (costula) reaching 6/10 of its length. Area petiolaris 1.6 × longer than wide. Hind femur 4.1–4.6 × longer than wide; hind metatarsus 0.6 × as long as hind tibia and 3.2 × longer than 2 nd hind tarsomere; hind claw with 3 basal teeth, mid tooth longest. Areolet pointed frontally; vein 2m-cu in its middle. Vein 1cu-a slightly postfurcal by 0.1–0.2 × its length. Postnervulus intercepted basad its middle. Pterostigma 3.0× longer than wide. Hind wing with 4 distal hamuli. Nervellus of hind wing vertical.
Metasoma. 1 st tergite slender, 3.0–3.5 × longer than wide. Postpetiolus with fine rugae apically. 2 nd tergite 1.2 × longer than wide, with few fine setiferous punctures. Thyridium transverse-oval. Ovipositor sheath (Fig. 23M) sparsely pilose, 9.3–10.0 × longer than wide, 0.5 × as long as hind tibia and 0.9 × as long as hind metatarsus, slightly narrowed in apical 0.2.
Color. Flagellum brown; scape, pedicel and basal flagellomere ochreous laterally. Face, clypeus and gena yellowish or reddish-yellow. Palps, mandible except teeth, malar space, facial orbit and ventral half of frontal orbit cream-yellow. Vertical orbit reddish. Frons medially, stemmaticum and occiput dorsally black. Pronotum creamyellow, collar black. Mesoscutum black or black with two paramedian yellowish stripes (in paratype); scutellum black, margins ± reddish or yellow. Mesopleuron yellow, with blackish central spot or stripe. Metapleuron yellow, with large central black spot. Propodeum yellow; area basalis, area externa and area dentipara black (in paratype also area superomedia). 1 st tergite black, red basally. 2 nd tergite black, with large triangular yellow spot in apical 2/3. 3 rd tergite black, with baso-median yellow spot in basal half. Following tergites yellow, with basal and apical brown spots. Ovipositor sheath brown. Fore and mid coxae and trochanters cream-yellow; fore and mid legs otherwise yellow. Hind coxa yellow, with brown dorsal spot. Hind femur red, ± black laterally; hind tibia red, widely black in basal 0.2 and apical 0.3. Hind tarsus red. Pterostigma dark brown.
♁: Body length 4.8–5.3 mm. Length of fore wing 4.6–4.8 mm.
Head. Flagellum with 33–39 flagellomeres; 1 st flagellomere 6.9–7.7 × longer than wide and 1.5–1.7 × longer than 2 nd flagellomere, 0.7-0.8 × as long as eye; 2 nd flagellomere 4.6–5.0 × longer than wide; preapical flagellomere 2.7 × longer than wide. OED 1.1 × and OOD 0.6 × ocellar diameter. Face (Fig. 12C) width 1.0 × combined length of face and clypeus and 0.9–1.0 × eye length. Malar space and ventral 0.5 of facial orbit striate. Malar space 0.5–0.8 × as long as width of mandibular base.
Mesosoma. Area superomedia 1.5–1.7 × longer than wide and 0.8–1.0 × as long as area petiolaris; anterior transverse carina (costula) reaching its middle. Area petiolaris 1.3–1.5 × longer than wide. Hind femur 4.2–5.0 × longer than wide; hind metatarsus 0.6 × as long as hind tibia and 2.4 × longer than 2 nd hind tarsomere; hind claw with 2–3 short basal teeth. Vein 1cu-a postfurcal by 0.2 × its length. Pterostigma 2.9–3.1 × longer than wide.
Metasoma. 1 st tergite 3.4–3.9 × longer than wide. Postpetiolus with fine punctures or rugae apically. 2 nd tergite 1.1–1.3 × longer than wide. Thyridium transverse-oval. Paramere rather long, 0.9–1.0 × as long as hind metatarsus, clubbed apically.
Color. Flagellum brown; scape and pedicel yellow ventrally. Head reddish-yellow. Palps, mandible except teeth, malar space, clypeus, face and ventral gena cream-yellow. Frons medially, stemmaticum and occiput dorsally black. Mesoscutum black, with lateral and paramedian reddish stripes. Scutellum yellow, with black basal spot. Pronotum and mesopleuron cream-yellow. Metapleuron cream-yellow, sometimes red and brown. Propodeum black in basal 2/3, reddish or yellowish apically. 1 st tergite black, reddish basally. 2 nd tergite black, with yellow band or triangular yellow spot in apical 0.2–0.3. 3 rd tergite black, with roundish or triangular baso-median yellow spot in basal 0.2–0.3. 4 th to 6 th tergites brown, lateral ochreous, sometimes with diffuse central transverse ochreous stripes. 7 th tergite brown dorsally, yellowish laterally. Fore and mid coxae and all trochanters cream-yellow; fore and mid legs otherwise yellow. Hind coxa yellow, with brown dorsal spot. Hind femur reddish, black laterally; hind tibia yellowish, widely black in basal 0.2 and apical 0.3. Hind tarsus red or brown. Pterostigma dark brown.
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 closely related to Mesochorus nigrofemur nov. sp. (e. g. strong median ridge of face, longer ventral mandibular tooth, similar carination of propodeum and color pattern of hind leg). It differs mainly by a paler mesosoma and slightly different color pattern of the metasoma. It is not impossible that both species represent intraspecific variants of the same taxon.
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 32-33, DOI: 10.11646/zootaxa.5245.1.1, http://zenodo.org/record/7673309