Tetractenion acaule Seyrig, 1932

Berry, Terry Reynolds & Noort, Simon van, 2020, Revision of the endemic Afrotropical genus Tetractenion (Hymenoptera, Ichneumonidae) with an identification key to genera of Banchinae for the region, ZooKeys 1007, pp. 49-84 : 49

Tetractenion acaule Seyrig, 1932 Fig. 1

Type material.

Lectotype ♀: Madagascar, Rogez, Forêt Cote Est, Muséum Paris, 1.31. A. Seyrig, EY9333, [White label with TYPE written in red] [Red type label]: Lectotype ♀ Tectractenion acuale , Seyrig, 1932, designated by Townes and Townes (1973), labeled by T. Yoshida, 2011 (MNHN) (photos of Lectotype examined: http://coldb.mnhn.fr/catalognumber/mnhn/ey/ey9333). Non-type ♀ (examined): Madagascar, Bekily, Reg. Sud. de L’ile, Feb 1930 and Jan-Feb 1931, Coll. Mus. Congo, Col. P.L.G. Benoit, Tectractenion acuale , det. P.L.G. Benoit, 1953 (RMNH). Additional material. ♀: Madagascar: Majunga Prov., Besalampy District, Marofototra dry forest, 17 km W of Besalampy, 4-11 February 2008, 16°43.30'S, 44°25.42'E, coll. M. Irwin, R. Harin’Hala, Malaise, dry wash in forest, elev. 170 ft MG-42A-20 (CASC).

Differential diagnosis.

Tetractenion acaule is immediately distinguishable from all other Tetractenion species by its unique color combination of a red mesosoma and a mostly black metasoma; distinct keels are present on outer mesoscutal lobes, the notauli do not reach the scutellum; metasomal tergite I has a distinct medial compression in the dorso-ventral view, tergite II have distinct gastrocoeli, and tergites IV-VIII are dorso-posteriorly weakly sclerotized, appearing as large membranous white areas on the dorsal surface. Tetractenion acaule closely resembles T. ibayaensis as both species are similar in color, having largely fulvous bodies with a white face and the hind femur infuscate, whereas the remaining Tetractenion species are largely yellow in color with yellow hind femora. Tetractenion acaule can easily be distinguished from T. ibayaensis by having a white gena and weakly sclerotized metasomal tergites IV-VIII; the head is narrow, straight behind the eyes; a distinct carina is present on the pronotal collar; distinct keels are present on the outer mesoscutal lobes, with the notauli not reaching the scutellum; pits on the mesopleuron and propodeum are shallow; metasomal tergite I is distinctly dorso-medially compressed; gastrocoeli on tergite II are distinct; tergites IV-VIII are postero-dorsally weakly sclerotized and white; and tarsal claws on the hind leg are simple. In T. ibayaensis the gena is brown and tergites IV-VIII are strongly sclerotized; the head is rounded behind the eyes; with no more than a wrinkle present on the pronotal collar; the mesoscutal lobes are hardly present, the notauli reach the scutellum; pits on the mesopleuron and propodeum are deep; metasomal tergite I is stout and indistinctly dorso-ventrally compressed in the medial region; gastrocoeli on tergite II are indistinct; and tarsal claws on the hind legs are pectinate.

Description

(updated from Seyrig 1932). Size 9-11 mm. Color: head white with a large black central area on occiput, reaching eyes on vertex and pointed on frons; antenna black, without pale ring; mesosoma red; metasomal tergites I and II red, though tergite II sometimes brownish, following tergites black with large membranous white areas from tergite IV; legs red, hind femur, tibia and tarsus infuscate; wings with sparse microtrichia, venation brown, pterostigma brown and centrally translucent reddish.

Head narrow, straight behind eyes; occiput deeply and angularly excavated, occipital carina strong, extending to lower gena at base of mandible; eyes very large; malar space almost half as long as mandibular basal width; face and clypeus finely, evenly and rather sparsely punctate on a shiny background; face with three lobes, tentorial pits deep; clypeus small, laterally convex with declivity, apically invaginated, with clypeal edge convex; mandibular teeth triangular, lower tooth longer than upper tooth; antenna long, slender and apically tapered.

Mesosoma stout; mesonotum deeply punctate, inter-punctuate spaces about as wide as punctures, rather matt, but not coriaceous; keels distinctly raised on outer mesoscutal lobes of mesoscutum, notauli abbreviated, not reaching the scutellum; apex of scutellum rounded; pronotum shining with a distinct thickened carina on collar, sparsely and very finely punctate; mesopleuron higher than wide, sparsely but more deeply punctate, speculum similarly punctate, background hardly shining, epicnemial carina ending at anterior edge of mesopleuron; shallow pits on mesopleuron and propodeum; metapleuron matt and deeply punctate; propodeum weakly convex, roughly punctate dorsally, punctate posteriorly confluently grading into transverse wrinkles, posterior transverse carina reduced, lateral longitudinal carinae present but faint, spiracle roundish-elliptic and small.

Metasoma hardly punctate at base of tergite II, indistinctly punctate beyond base; tergite I elongate, more than twice as long as wide, tapered anteriorly, glymma present, spiracle positioned slightly in front of middle and protruding, especially dorsally, with a distinct medial depression dorso-ventrally; tergite II longer than wide or subquadrate with gastrocoeli distinct; tergite III quadrate to transverse; metasomal tergites IV-VIII moderately laterally compressed; ovipositor sheath concealed or hardly protruding.

Fore wing without ramellus on Rs-M vein; Rs hardly sinuate; areolet large and quadrate with a short stalk receiving 2m-cu at center. Hind wing with Cu1 shorter than cu-a such that Cu2 arises above the middle of these combined veins. Legs very long; hind femur reaching beyond metasomal apex; length of tibia III plus tarsus III as long as body; spurs of tibia III longer than half metatarsal length; tarsal claws on hind leg simple.

Male hardly different: temples a bit less narrowed behind eyes, metasomal tergite II entirely black.

Distribution.

Madagascar.

Figures

Figure 1. Tetractenion acaule Lectotype (MNHN) A habitus, lateral view B habitus, dorsal view C head, anterior view D data labels. Photographs of lectotype RECOLNAT (ANR- 11 - INBS- 0004) - Christophe Herve - 2014. http: // coldb. mnhn. fr / catalognumber / mnhn / ey / ey 9333 (used with permission of Agniele Touret-Alby - Curator of Hymenoptera MNHN).