Peucobius Townes, 1971

Khalaim, Andrey I., Ruiz-Cancino, Enrique & Coronado-Blanco, Juana Maria, 2023, Taxonomy of the genus Peucobius Townes (Hymenoptera, Ichneumonidae, Sisyrostolinae), Journal of Hymenoptera Research 95, pp. 245-260 : 245

Genus Peucobius Townes, 1971

Type species.

Peucobius fulvus Townes, 1971, by original designation.

Comparative diagnosis.

Peucobius can be distinguished from all other genera of Sisyrostolinae by the combination of the following characters: 1) fore wing without areolet, i.e. vein 3rs-m absent (Fig. 18 ) (areolet present in Brachyscleroma ); 2) tarsal claws simple (pectinate in Laxiareola ); 3) anterior transverse carina of propodeum present (Fig. 3 ) (carina absent in Melanodolius and some species of Erythodolius ); 4) clypeus unspecialized, evenly rounded in profile, without a transverse ridge, medial point or multiple or medial crenulations (Figs 5 , 15 ) (transverse ridge present in Lygurus ; medial point present in some species of Erythrodolius ; medial crenulations present in some species of Erythrodolius and Icariomimus ).

Within Sisyrostolinae , Peucobius has the smallest species with fore wing length 2.5-3.0 mm, while the genus with the next smallest species, Lygurus , has fore wing length 4.0-5.0 mm, and some other genera are much larger (e.g., 7.0-19.0 mm in Erythrodolius and 17.0-30.0 mm in Melanodolius ).

Description.

Small insects with fore wing length 2.5-3.0 mm. Head and mesosoma mostly finely granulate to subpolished, impunctate or partly with fine punctures. Head, in dorsal view, with gena strongly rounded posterior to eyes. Clypeus wide, 2.5-3.5 times as broad as long, lenticular, weakly convex, more or less flat medially, with a row of long fine setae on lower margin. Mouthparts short, unspecialized; maxillary and labial palp formula 5+4. Mandible bidentate, with teeth subequal by length or either upper or lower tooth somewhat longer than other. Malar space 0.8-1.0 times as long as basal mandibular width, with scabrous area between eye and mandibular base. Flagellum filiform, with 14-17 flagellomeres. Epomia absent. Notaulus short or absent. Scutellum with lateral longitudinal carinae very short. Sternaulus absent or as weak impression ventrolaterally in anterior part of mesopleuron. Epicnemial carina present. Posterior transverse carina of mesopleuron absent. Propodeum more or less fully carinate (as in Fig. 3 ), sometimes carinae partly obliterated. Fore wing as in Fig. 18 ; areolet absent, pterostigma relatively large, vein 2m-cu with one large bulla. Hind wing with nervellus (cu1&cu-a) intercepted below centre. Legs slender; fore tibia with a tooth-like projection on distal outer side; tarsal claws not pectinate. First metasomal tergite 1.8-2.5 times as long as posteriorly broad, with large glymma at base. Second tergite transverse; thyridum (if discernible) very small, oval, at base of tergite 2. Laterotergites 2 and 3 not separated by crease. Ovipositor long and slender, weakly upcurved, slightly swollen before apex (Fig. 11 ).

Remarks.

In addition to two previously known Nearctic species of Peucobius , one species from Central Mexico and one from Japan are described. A distribution map (Fig. 27 ) of three North American species and identification key to the four species of Peucobius occurring in the world are given below. We also provide a key to a new species of Peucobius discovered from the East Palaearctic region and two species of the morphologically similar genus Lygurus .

The new species from Mexico differs well from two other North American species, P. fulvus and P. piceus (see the key below). Peucobius fulvus and P. piceus are known to us from their original descriptions ( Townes 1971) and several specimens from USA and Canada. The length of mandibular teeth is found to work well for distinguishing these morphologically very similar species from each other, while the two features provided by Townes (1971), i.e. sculpture of mesoscutum and colouration of hind coxa, are less reliable and therefore must be used with caution.

Figures

Figure 27. Distribution map of P. fulvus (red), P. bennetti sp. nov. (blue) and P. piceus (green) in North America.

Figures 18 - 20. Peucobius shimizui sp. nov., holotype female 18 wings 19 metasoma, dorsal view 20 ovipositor, lateral view.

Figures 1 - 3. Peucobius fulvus, female (Canada, Ontario) (1) and P. piceus, female (USA, Colorado) (2, 3). 1, 2 habitus, lateral view 3 propodeum, dorsal view.

Figures 4 - 11. Peucobius bennetti sp. nov., holotype female 4 body, lateral view 5 head, front view 6 clypeus and mandibles, antero-ventral view 7 head and mesoscutum, dorsal view 8 mesosoma and base of metasoma, lateral view 9 fore wing 10 propodeum, dorsal view 11 apex of ovipositor, lateral view.

Figures 12 - 17. Peucobius shimizui sp. nov., holotype (11, 13 - 15) and paratype (12, 16) females 12 habitus, lateral view 13 antenna 14 head, dorsal view 15 head, front view 16 head and mesosoma, lateral view 17 propodeum, dorsal view.