Tetragonula

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 : 23-24

Key to Species Groups of Tetragonula s.str.

(worker caste)

Note that these groups are seemingly not natural, with the possible exception of the carbonaria -group ( Rasmussen & Cameron, 2010). Accordingly, these groups are merely a convenience for aiding identification through the exclusion of blocks of diversity in this complicated and large genus, and should not be considered as representing natural groups from which evolutionary hypotheses can be based. Once the genus is comprehensively revised and a more extensive robust phylogeny including all of the known species is produced, then natural species groups should be circumscribed to aid the identification of these bees. For the time being, two groups of Sakagami (1978) — the gressiti -group and geissleri -group — are considered synonymous with the laeviceps -group. The key is adapted from Sakagami (1978) and Dollin et al. (1997).

1. Mesepisternum posteriorly sparsely setose, contrasting with rather densely setose anterior portion and metepisternum ( Fig. 36 ); malar space linear or nearly so ( Figs. 20 , 32 ) ............................................................................................................ 2

—. Mesepisternum and metepisternum densely and evenly covered with fine short setae; malar space developed, not linear [mesoscutal setal banding present, albeit sometimes poorly defined] ..................................................... carbonaria -group

2(1). Small bees, forewing including tegula 3.0–4.0 mm; mesoscutum with distinct setal bands separated by broad glabrous interspaces ............... iridipennis -group

—. Larger bees, forewing including tegula 3.9–4.8 mm; mesoscutum rather evenly setose (e.g., Fig. 38 ) .............................................................................. laeviceps -group

Figures

Figures 35–39. Workers of Tetragonula (Tetragonula) florilega, new species. 35. Dorsal view of head and oblique dorsal view of mesosoma (NIGP 176093). 36. Mesosoma in profile, with arrow indicating largely bare posterior surface of mesepisternum relative to the more abundant, appressed, white, plumose setae of the anterior portion (AMNH Zh-001). 37. Wing venation (SEMC F002514). 38. Oblique dorsal view of mesosoma, noting uniform setation (NIGP 176124). 39. Expanded detail of leading edge of hind wing showing distal hamuli (SEMC F002514).

Figures 18–22. Photographs of workers of modern Tetragonula Moure. 18. Dorsal habitus of Tetragonula (Tetragonula) malaipanae Engel, Michener, & Boontop from Thailand. 19. Lateral habitus of T. (T.) malaipanae. 20. Facial view of T. (T.) malaipanae. 21. Facial view of T. (Tetragonilla) collina (Smith) from Thailand. 22. Lateral habitus of T. (T.) collina.

Figures 32–34. Worker (NIGP 176093) of Tetragonula (Tetragonula) florilega, new species, µCT scans. 32. Facial view. 33. Prolateral view of metatibia and metatarsus. 34. Retrolateral view of metatibia and metatarsus.