Trissoscelio Kieffer, 1917

Talamas, Elijah J., Awad, Jessica, Tortorici, Francesco & Johnson, Norman F., 2024, Platygastroidea in the Oxford University Museum of Natural History: taxonomic updates and a photographic catalog of type specimens, Insecta Mundi 2024 (30), pp. 1-16 : 10-11

Trissoscelio Kieffer , revised status

Trissoscelio Kieffer, 1917: 52 (original description. Type: Trissoscelio nigriceps Kieffer , by original designation. Key to species); Kieffer, 1926: 419 (description, keyed, key to species); Muesebeck and Walkley, 1956: 407 (citation of type species); Baltazar, 1966: 181 (cataloged, catalog of species of the Philippines); Masner, 1976: 45 (junior synonym of Opisthacantha Ashmead ).

Comments. Trissoscelio is widespread in the Old World, primarily in the tropics. A very large number of species are apparent, and the limits of the genus are not fully established. A robust delimitation of Trissoscelio as a monophyletic taxon will require critical review of numerous genera that appear closely related to it and may be congeneric. Some of these genera are micropterous forms that exhibit a general reduction in external characters, suggesting the need for molecular data to untangle homoplasy from shared ancestry. Named genera in this category include Chakra Rajmohana and Veenakumari , Anokha Rajmohana and Veenakumari , Apteroscelio Kieffer , Platyscelidris Szabó , Jarabambius Galloway and Lidgbirdius Galloway. Resolution of relationships between these taxa is well beyond the scope of this publication. However, we have gathered enough data to confidently propose that Trissoscelio should be removed from synonymy with Opisthacantha Ashmead as a prelude to a more comprehensive revision.

Justification for resurrection. Trissoscelio was treated as a junior synonym of Opisthacantha by Masner (1976). Both genera are characterized by the absence of a hyperoccipital carina; 12-merous antennae in both sexes; mesoscutellum without medial or lateral processes; metascutellum with 1–3 medial processes (variously called spines, teeth, plates, or more generally armature); fore wings with typical venation, i.e., submarginal, marginal, postmarginal and stigmal veins; and hind wings with a complete submarginal vein extending from the base of the wing to the hamuli. These two genera can be separated by the number of metasomal segments visible in females (excluding those extruded with the ovipositor): six in Trissoscelio , and seven in Opisthacantha . This difference in the number of visible tergites corresponds with their ovipositor types: a telescoping, Scelio - type ovipositor in Trissoscelio ( Fig. 10 ) and a non-telescoping, Ceratobaeus - type in Opisthacantha . (See Austin and Field 1997 for a discussion of these structures.) Trissoscelio does not have a skaphion, whereas this structure is found in nearly all Opisthacantha . Notauli are often found in Opisthacantha but are usually absent in Trissoscelio ; there are very rare exceptions in Trissoscelio in which the notauli are weakly indicated posteriorly.

The molecular analysis of Chen et al. (2021) retrieved Trissoscelio and Opisthacantha in disparate parts of the phylogeny. Trissoscelio was in a clade of genera of with Scelio -type ovipositors, and Opisthacantha groups with a clade of genera with Ceratobaeus -type ovipositors, congruent with the treatment of this character as invariant within a genus. Although we would prefer to resurrect Trissoscelio in the context of a revision, we also prefer not to delay this act any further. Images are available for the holotype of the type species ( T. nigriceps , Figs 4–6 ), and with topotypical specimens that are conducive to photography, the genus can be diagnosed from Opisthacantha . There is also a need to transfer species from Opisthacantha because, at present, it is almost certainly a polyphyletic taxon.

Figures

Figures 10–12. Trissoscelio nigriceps, female, fresh specimen collected from the type locality.10) Head, mesosoma, metasoma with extruded ovipositor system, dorsal view. 11) Head, anterolateral view. 12) Head, ventrolateral view.

Figures 4–6. Trissoscelio nigriceps, holotype male (MNHN 0080). 4) Head, anterior view. 5) Head and mesosoma, lateral view. 6) Head, mesosoma, metasoma, dorsal view.