Palaeometopius eocenicus Menier et al., 2004

Viertler, Alexandra, Klopfstein, Seraina, Jouault, Corentin & Spasojevic, Tamara, 2022, Darwin wasps (Hymenoptera, Ichneumonidae) in Lower Eocene amber from the Paris basin, Journal of Hymenoptera Research 89, pp. 19-45 : 19

Palaeometopius eocenicus Menier et al., 2004

Figs 1 , 2

Systematic placement.

Menier et al. (2004) placed their monotypic genus in Metopiinae , stating that it "shares the main diagnostic characters of the Metopiinae , as defined by Townes (1971) ". Examining the holotype at MNHN.F, we found the evidence for such a placement unconvincing. This has already been indicated by the list of characters mentioned by the original authors as differing between the fossil and all other Metopiinae . In fact, this subfamily is one of the very few among Ichneumonidae that has a unique character to define it: the upper margin of the face is extended as a triangular process between the antennal sockets. While Menier et al. (2004) mentioned that his process was shorter in the fossil than in the extant species of the subfamily, we could not find any trace of it. Several other characters disagree with a placement in Metopiinae , including the long notauli that meet medially on the mesoscutum in the fossil; the strongly inclivous vein 2m-cu in the forewing with two widely separated bullae; and finally, the rather long ovipositor.

In contrast, all the characters visible in the fossil are in accordance with a placement in Tryphoninae , especially the strong and complete propodeal carination, the broad first tergite, the strongly convergent notauli, and the stout ovipositor, lacking a distinct nodus or dorsal subapical notch. Also, none of the characters in the fossil are entirely absent from extant Tryphoninae , although some, such as the twisted mandibles and the clearly protruding ovipositor, are rather rare (other than in Netelia Gray, 1860. However, the combination of characters shown in the fossil is not in accordance with any of the extant tribes ( Bennet 2015). There are two apomorphic characters uniting extant Tryphoninae , the stalked egg, which is often carried exposed on the ovipositor, and a fringe of long, parallel setae on the clypeus. Neither are visible in the fossil, either due to absence or just preservation or poor visibility. We thus label our placement of this fossil in Tryphoninae as tentative.

Material examined.

France • Holotype female; Oise department, region of Creil, Chevrière, Le Quesnoy; 49°20'06.0"N, 2°40'28.9"E; G. De Ploëg leg.; in amber mounted in Canada balsam; MNHN.F. A30079 (PA2439).

Type condition.

Nearly complete specimen; apical part of right and median part of left antenna, right foreleg from tibia and apex of left fore tibia missing; wings folded over metasoma, obscuring view on tergites; milky substance present ventrally from metasoma, thus in part obscuring view on sternites. Cuticula translucent in most places, interior partly hollow, organs partly preserved.

Description.

Body 5.6 mm. Colour or colour pattern not visible.

Head. Mandibles long and overlapping, curved along main axis and strongly twisted; bidentate, with lower tooth about half as long as upper one. Labrum concealed below clypeus. Clypeus somewhat convex in profile, probably weakly separated from face; apical margin truncate medially, curved upwards laterally. Malar space clearly longer than mandibular width at base. Anterior tentorial pits distinct. Shape of face difficult to discern, but probably rather flat with weak median swelling. Eyes in profile about 0.8 × height of head. Upper margin of face without process, without modification between antennal sockets. Frons without strong impressions for scape. Ocelli of normal size. Maxillary palp with five segments, labial palp not entirely visible. Scape slightly longer than wide; truncation strongly oblique, forming an angle of about 45° with the main axis. Pedicel much shorter and smaller than scape. Antenna 4.2 mm, with 25 flagellomeres, evenly thick throughout entire length; first flagellomere 3.2 ×, subapical flagellomere 1.1 × as long as wide.

Mesosoma. Pronotum rather short, well visible around front half of mesoscutum when viewed from above; without modification at base of notaulus; with at least dorsal part of epomia present. Mesosternum with deep scrobe with cross-carinulae; posterior transverse carina absent. Sternaulus deeply impressed anteriorly, seemingly reaching only to about 0.4 × length of mesopleuron. Epicnemial carina complete ventrally, dipped in mesosternal scrobe; laterally forming two widely spaced, strong curves; upper end not discernible. Mesopleuron only visible at angle, rather short; with short impression at around mid-height in front, where epicnemial carina shows a second curve above the one accommodating the sternaulus; mesopleural furrow not discernible. Notauli deeply impressed, with some cross-carinulae in the impression; strongly converging, meeting in an impressed area medially on mesoscutum. Scutellum short and wide, without lateral carinae; metanotum of normal length and convex. Submetapleural carina complete, pleural carina not visible. Propodeum in profile somewhat shortened; carination complete, with latero-median- and lateral longitudinal carinae, anterior and posterior transverse carinae; all carinae strongly angled at meeting points; area basalis very much shortened, area superomedia wider than long, area petiolaris with an additional median longitudinal carina nearly as strong as remaining carinae. Hind margin of propodeum simple. Legs simple, coxae simply convex; fore tibia simple to slightly enlarged, mid and hind tibiae with two spurs; hind coxa evenly rounded, a little longer than wide. Hind tarsomeres deeply excised on dorsal side. Claws short and stout, simple, arolium shorter than claws.

Wings. Fore wing 4.8 mm. Areolet closed, pentagonal-oblique, 3rs-m with one bulla, about as long as 2 + 3M, 4M very short. 2m-cu inclivous and strongly bowed outwards, with two small, about evenly spaced bullae. 4Cu nearly twice as long as 5Cu. 4Rs straight. 1Rs + M about as long as width of surrounding veins. 1cu-a at junction of M + Cu and 1M or nearly so. Pterostigma 4.0 ×, cell 2R1 2.5 × as long as wide. 5M entirely tubular. 2Cu 0.8 × of 1M + 1Rs, 0.85 × of r-rs. 1m-cu & 2Rs + M angled. 3Cu clearly longer than 2cu-a. Hind wing with M + Cu complete, slightly curved on entire length. 1Cu about 0.6 × cu-a. 1Rs about 1.5 × rs-m, although upper end hardly discernible.

Metasoma. Sternites poorly visible, weakly sclerotized; hypopygium short, transverse, appears weakly sclerotized. T1-T4 depressed, apex of metasoma about circular. T1 poorly visible, appears subquadrate, evenly tapering anteriorly in dorsal view; spiracle seems around middle; latero-median carina seems present, widely parallel. T2 transverse, appears normally separated from T3. T4 and T5 well developed; T6 and following tergites very short and hidden below anterior tergites. T8 short, not elongated in horn or boss. Ovipositor sheaths about 0.7 mm, evenly setose, parallel, then tapering from about mid length. Ovipositor tip region rather long, evenly tapering, without discernible teeth.

Figures

Figure 1. Holotype of Palaeometopius eocenicus Menier et al., 2004 A dorsal view of whole specimen B ventral view of whole specimen C front view of face D dorsal view of propodeum E ovipositor and ovipositor sheaths F epicnemial carina on ventral side. Scale bars: 2 mm (A, B); 1 mm (C, D); 0.5 mm (E, F).

Figure 2. Interpretative line drawings of the wings of Palaeometopius eocenicus Menier et al., 2004 with venation nomenclature in black and cell nomenclature in grey A fore wing B hind wing. Scale bar: 1 mm (A, B).