Mesochorus (Stictopisthus) longistylus, Riedel, 2023

Riedel, Matthias, 2023, Contribution to the taxonomy of the Southeast Asian Mesochorinae (Hymenoptera, Ichneumonidae), Zootaxa 5245 (1), pp. 1-72 : 20

Mesochorus (Stictopisthus) longistylus nov. sp.

( Figs 3E , 10C, 10D , 18C )

Holotype. (♁) Malaysia: Sabah, Kinabalu Park Head Q., 8–11.iii.1987, c 1900 m, Malaise trap 5, C. v. Achterberg, RMNH´87 (Leiden).

Etymology. The species name refers to the long paramere (“stylet” in the traditional terminology of authors, e. g. Schwenke 1999).

Description. ♁: Body length 5.3 mm. Fore wing 3.8 mm.

Head. Flagellum with 32 flagellomeres; 1 st flagellomere 7.5 × longer than wide and 1.6 × longer than 2 nd flagellomere, 0.8 × as long as eye; 2 nd flagellomere 4.7 × longer than wide; preapical flagellomere 2.7 × longer than wide. Occipital carina complete medially. Temple slightly and roundly narrowed behind eye, dorsally 0.6 × as long as eye. OED 1.8 × and OOD 0.7 × ocellar diameter. Frons ( Fig. 10D ) dorsally with fine transverse striation and with two long curved paramedian ridges above and between antennal sockets. Face ( Fig. 10C ) including facial orbit coarsely punctate, slightly convex, width 1.0 × combined length of face and clypeus and 1.1 × eye length; inner eye margins parallel ventrally. Subantennal transverse carina not dipped medially. Malar space with fine striae. Malar space 0.6 × 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 . 1.8 × longer than high. Side of pronotum largely smooth, with few very sparse punctures. Notaulus indistinct. Mesoscutum with rather dense punctures, shining. Mesopleuron with dense punctures fronto-dorsally and with coarse but rather dense punctures ventrally, speculum smooth. Dorsal end of epicnemial carina separated from frontal margin of mesopleuron. Metapleuron densely punctate; juxtacoxal carina absent; submetapleural carina moderately lamelliform. Scuto-scutellar groove 3 × wider than long, smooth. Scutellum slightly rounded in profile, almost smooth. Propodeum ( Fig. 18C ) completely carinate, except confluent area basalis and area superomedia. Area basalis and area superomedia with distinct transverse rugae. Area superomedia c 1.8 × longer than wide and 1.6 × longer than area petiolaris; anterior transverse carina (costula) reaching frontal to its middle. Area petiolaris 1.3 × wider than long. Hind femur 4.6 × longer than wide; hind metatarsus 0.6 × as long as hind tibia and 2.3 × longer than 2 nd hind tarsomere; hind claw apparently simple. Areolet shortly sessile frontally; vein 2m-cu in its middle. Vein 1cu-a postfurcal by 1.0 × its length. Postnervulus intercepted in its middle. Pterostigma 3.1 × longer than wide. Distal part of RA (metacarp) long, about as long as width of pterostigma. Hind wing with 4 distal hamuli. Nervellus of hind wing vertical.

Metasoma. 1 st tergite slender, 3.5 × longer than wide. Postpetiolus with coarse longitudinal rugae. 2 nd tergite 1.4 × longer than wide. Thyridium transverse-oval. Paramere long, 1.0 × as long as hind metatarsus, clubbed apically.

Color. Antenna reddish-brown. Head reddish-yellow. Palps, mandible except teeth, clypeus, malar space, ventral gena, facial orbit and ventral half of frontal orbit cream-yellow. Stemmaticum blackish. Pronotum and tegula creamyellow. Mesopleuron and metapleuron yellow. Mesoscutum reddish-yellow, with two lateral and one antero-medial brown stripes. Scutellum reddish-yellow. Propodeum blackish, area externa and area petiolaris dark reddish. 1 st tergite black, dark reddish basally. 2 nd tergite black, with yellow band in apical 0.2. 3 rd tergite brown, with triangular yellow basally. Following tergites brownish. Fore and mid legs including coxae and trochanters cream-yellow. Hind leg yellowish; hind tibia black in apical 0.1; hind tarsus except yellow metatarsus blackish. Pterostigma hyalineyellow.

♀ unknown.

Taxonomical remark. The species belongs to the subgenus Stictopisthus and is characterized within this subgenus by its large size, lateral striation of frons, and the confluent and transversely rugose area basalis and area superomedia.

Figures

FIGURE 3. Oriental Mesochorinae, habitus from lateral.A−Mesochorus harlequinus n. sp. HT, B−M. kinabaluensis n. sp. HT, C−M. lamdongensis n. sp., D−M. longimurus n. sp. HT, E−M. longistylus n. sp. HT, F−M. longivalvator n. sp. HT.

FIGURE 10. Oriental Mesochorinae, face from frontal. A− Mesochorus lamdongensis n. sp. HT, B−M. longimurus n. sp. HT, C−M. longistylus n. sp. HT, D−M. longistylus n.sp. (frons from dorsal), E−M. longivalvator n. sp. HT, F−M. malaysiacus n. sp. HT, G−M. malucutus n. sp. HT, J−M. nigripleuris n. sp. HT.

FIGURE 18. Oriental Mesochorinae, propodeum from dorsal. A− Mesochorus kinabaluensis n. sp. HT, B−M. longimurus n. sp. HT, C−M. longistylus n. sp. HT, D−M. malaysiacus n. sp. HT, E−M. malucutus n. sp. HT, F−M. nigripleuris n. sp., G−M. nigromaculatus n. sp. HT, H−M. pictiloides n. sp. HT, I−M. pterostigmator n. sp.