Tetragonula Moure

Engel, Michael S., Herhold, Hollister W., Davis, Steven R., Wang, Bo & Thomas, Jennifer C., 2021, Stingless bees in Miocene amber of southeastern China (Hymenoptera: Apidae), Journal of Melittology 2021 (105), pp. 1-83 : 22-23

Subgenus Tetragonula Moure

Tetragonula Moure, 1961: 206 . Type species: Trigona iridipennis Smith, 1854 , by original designation.

Flavotetragonula Shanas in Shanas & Faseeh, 2019: 34. Type species: Tetragonula (Flavotetragonula) calophyllae Shanas & Faseeh, 2019 , by original designation. Synonymy vide Engel (2019).

The subgenus Tetragonula comprises the bulk of diversity within the genus as well as all Asian-Malesian-Papuasian Meliponini , with at least 31 species. Tetragonula is quite distinctive and was recognized as a group, albeit more informally as the “iridipennis-group” or “ Tetragonula -group” (variably including Tetragonilla ), even when it was lumped under Trigona or Heterotrigona (e.g., Sakagami, 1978; Michener, 1990, 2007; Dollin et al., 1997). The subgenus is easily recognized by the combination of the basal sericeous area of the proximal superior retrolateral surface of the metabasitarsus and the thickened and rounded mesoscutellum overhanging the metanotum and partially the propodeum, along with the slightly convex retromarginal metatibial contour bearing a subangulate superior distal angle, a narrowly open marginal cell apex, a uniformly colored forewing membrane, a scape that is shorter than the torulocellar distance, and a rastellum composed of soft setae, among other traits.

The proposal of a new subgenus for T. (T.) gressiti (Sakagami) and species putatively similar to it ( Shanas & Faseeh, 2019) renders Tetragonula s.str. paraphyletic ( Rasmussen & Cameron, 2010) and should be avoided, particularly as the proposed differences are exceptionally minor and somewhat subjective distinctions in wing venation or wing microtrichia. For example, the putative patch, narrower than 1Rs, beneath the juncture of 1Rs and the pterostigmal base is exceptionally variable, not only across Indomalayan Tetragonula , but even in some species between individuals within a nest. Furthermore, the present fossil species intermingles some of the traits between their subgenus and Tetragonula s.str., demonstrating the failure of these characters to distinguish natural groups in Tetragonula s.str. Shanas & Faseeh (2019) also failed to recognize that the stub sometimes present at the apical bend of Rs is Rs 2 (beyond Rs 1 or 2r-rs), needlessly proposing a term (unculus) for this abscissa.