Petiolon Kasparyan, 2020

Kasparyan, D. R., 2020, A new ichneumonid genus (Hymenoptera: Ichneumonidae: Ctenopelmatinae) from the south of Russian Far East, Zoosystematica Rossica (China) 29 (2), pp. 296-300 : 297-299

Genus Petiolon Kasparyan , gen. nov.

( Figs 1–8)

Type species: Petiolon cephalotes Kasparyan , sp. nov.

Comparative remarks. The genus Petiolon is described in the tribe Pionini as it has a distinct tooth at the apical edge of the fore tibia (typical of all Ctenopelmatinae ); narrow U-shaped groove between the metanotum and propodeum; a very thin ovipositor apex without a dorsal subapical notch ( Fig. 6); open clypeal fovea; distinct notauli; and the cercus twice as long as wide. The enlarged head of Petiolon is similar to that in some Perilissini, but its first metasomal tergite is without glymmae ( Fig. 4), which are always present in Perilissini.

Petiolon may be distinguished from other genera of Pionini by its broad ovipositor sheath and thick subcylindric and slightly upcurved ovipositor with the dorsal valve tapering and narrow only at the extreme apex (in apical 0.1) ( Fig. 6), and the forewing with the subcostal and basal veins meeting at a very acute angle ( Fig. 1). Petiolon resembles the endemic Chilean genus Petilium Townes, 1970 in having the prepectal carina distant from the anterior edge of the mesopleuron, and a very notable first metasomal segment with a long and straight petiole and spiracles situated just behind the middle of the tergite ( Fig. 4). The new genus is also characterised by a notably slender body and large head; the latter is 1.7 times as wide as the mesoscutum, and the distance between the lateral ocellus and eye is at least 3.0 times the maximum diameter of the lateral ocellus ( Fig. 2).

Description. Head large, 1.7 times as wide as mesoscutum (measured between tegulae). Lateral ocellus separated from eye by about 3.0 times its own maximum diameter ( Figs 2, 3). Clypeus almost flat, hardly separated from face by superficial impression, with lower margin weakly arcuate, obtuse, truncated and slightly projecting centrally; anterior edge of truncation rather sharp, and hind edge of truncation straight and sharp. Mandible with equal teeth; its lower margin in basal 0.65 sharp, carinate. Occipital carina joining hypostomal carina very close to base of mandible (oral carina about 0.1 times as long as basal mandibular width).

Head, thorax, hind coxa and hind femur smooth and evenly covered with dense distinct punctures; lower part of clypeus polished, with sparse punctures; mesopleuron with large impunctate speculum; metapleuron with small polished area just before anterior end of pleural carina of propodeum. Propodeum with punctures somewhat smaller and shallow, its posterior areas impunctate.

Epomia vertical and short. Upper end of prepectal carina distant from front edge of mesopleuron. Notaulus short and sharp at anterior vertical part of mesoscutum. Propodeum separat- ed from hind margin of metanotum by a deep and narrow U-shaped groove. Carinae of propodeum complete, costulae present ( Fig. 5). Fore wing with basal vein and subcosta joining at very acute angle about 20° ( Fig. 1). Areolet present, receiving second recurrent vein close to its outer corner; nervulus vertical and almost opposite basal vein. Hind wing with nervellus inclivous and intercept- ed at its lower 0.2. Apical edge of front tibia dorsally with a distinct tooth. Membranous flap on inner side of front tibial spur ending distally in a gradual taper. Longest spur of hind tibia straight, about 0.3 times as long as hind basitarsus. Tarsal claws with two or three sparse teeth in middle part and three or four close teeth at base ( Fig. 8).

First segment of metasoma without glymmae, narrow, 3.3 times as long as broad, with spiracle slightly behind its middle (in apical 0.45) ( Fig. 4); its median and dorsolateral longitudinal carinae absent; petiole almost straight in lateral view, flat dorsally and laterally, rectangular in cross-section (about 1.2 times as high as wide) near its middle. Second tergite basolaterally with distinct thyridium ( Fig. 4). Tergites smooth, first tergite with moderately small and irregular punctures, and subsequent tergites with punctures very small and dense. Epipleurae of tergites two and three separated by crease and turned under. Hind margin of tergite six dorsally with a broad median membranous emargination ( Fig. 7). Ovipositor sheath 0.55 times as long as apical depth of metasoma, rather wide, upcurved, with apical fringe of setae. Ovipositor thick, subcylindrical, without subapical dorsal notch, slightly upcurved, with upper valve thin and wedge-shaped in apical 0.1; low- er valves very thin in apical 0.25 and projecting beyond apex of upper valve ( Fig. 6). Cerci about twice as long as wide.

Etymology. The generic name is derived from the Latin petiolus (petiole), referring to the very slender petiole of the first metasomal segment. The gender is masculine.

Composition. The genus comprises a single species which is described below.