Engel, Engel & Herhold & Davis & Wang & Thomas, 2021

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 : 20-21

Genus Tetragonula Moure

The genus Tetragonula is the most diverse and widespread of the lineages of Asian Meliponini ( Figs. 18–22 ), extending from northwestern India to Sri Lank in the west, across Southeast Asia to Yunnan in the north, southward throughout mainland Southeast Asia, across Malesia (north to Camiguin) and Papuasia to eastern Santa Isabel in the Solomon Islands (although it likely also extends to San Cristobal), and across northern and eastern Australia ( Fig. 23 ). The genus is challenging for the presence of many cryptic species (e.g., Sakagami, 1978; Franck et al., 2004; Engel et al., 2017; M.S.E., pers. obs.), distinguished by seemingly trivial morphological differences or morphometrics but distinct in terms of their nesting biology and perhaps also ecology. Thus, while there are already a large number of species, this diversity may grow as further data are gathered.

Two subgenera are recognized among the modern fauna ( Figs. 18–22 ): Tetragonilla , with four species, and the remainder in Tetragonula s.str. (Rasmussen et al., 2017; Engel et al., 2018). Although some authors have considered these two groups to be distinct genera (e.g., Moure, 1961; Rasmussen, 2008), the distinctions between them are fairly minor and it seems more beneficial to treat them as reciprocally monophyletic subgenera of a single, more broadly circumscribed genus. Indeed, when united together, Tetragonula in this sense is easily diagnosed and separated from other Asian genera (Rasmussen et al., 2017; Engel et al., 2018).

Interestingly, a single species of Tetragonula is relatively common in Zhangpu amber, analogous to the situation of Proplebeia in Dominican and Mexican ambers. The species is assigned to the nominate subgenus.

Figures

Figure 23. Map depicting modern day distributions of Tetragonula Moure (green line) and Austroplebeia Moure (red line) in relation to the deposits at Zhangpu (red star). Map produced using Shorthouse (2010).

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.