Scaptotrigona Moure
Creators: name: Engel, Michael S.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Apidae
Scaptotrigona

description: Genus Scaptotrigona Moure
An arrangement is established herein that reclassifies some of the previously outlined species groups as subgenera. As noted above, the bipunctata and luteipennis groups (sensu Engel, 2022a) are abandoned, some of their species moved to other groups, and the remainder classified as a subgenus. It is hoped that this arrangement might make it easier for others working on the biology of these bees to identify the taxa they are exploring, but greatly narrowing the available options.
The analysis of Roubik et al. (1997) indicated a sister-group relationship between Scaptotrigona and Meliwillea Roubik et al., based on the presence of tomentum on the metasomal terga and the occurrence of wavy setae on the sterna. The elongate, wavy, metasomal setae are abundant in Scaptotrigona, while in Meliwillea they are certainly present but not to the same degree as in the former. The tomentum present in Meliwillea is not at all like that of the postica group (i.e., Scaptotrigona s.str. as treated herein), where the tomentum is yellowish and densely covers metasomal terga III–V. Instead, in Meliwillea the white to off-white tomentum is diffuse and, when not worn, is to be found more laterally on terga V and VI. This condition is best approximated by species of the subgenera Eoscaptotrigona and to some degree Baryorygma, and is likely plesiomorphic for Scaptotrigona s.l. Assuming for the moment that the combination of diffuse tomentum on terga IV–VI and scatered, short, suberect, metasomal bristles of Eoscaptotrigona are symplesiomorphic with those found in Meliwillea, then I would hazard to assert that the distribution of characters among other Scaptotrigona tends to suggest the following working hypothesis of relationships: Eoscaptotrigona + [Sakagamilla + {Dasytrigona + Gymnotrigona + (Astegotrigona + Baryorygma + Scaptotrigona)}]. Naturally, an extensive analysis is needed to determine whether such an initial hypothesis accords with a broad array of character data, and so I would not presume that the aforementioned ordering is anything other than informed speculation.
Key to Subgenera of Scaptotrigona
(worker caste only)
1. Bristles of vertex, mesoscutum, and mesoscutellum long, distinctly longer than median ocellar diameter (Engel, 2002a: fig. 1) ....................................................... 2
—. Bristles of vertex, mesoscutum, and mesoscutellum short, distinctly shorter than median ocellar diameter (Engel, 2002a: fig. 2) ................. Sakagamilla Moure
2(1). Scape and supraclypeal area without minute, erect to suberect bristles, at most sometimes with one or two bristles at extreme base of scape, otherwise setation minute and appressed (Figs. 4–6); tergal setation not as below; integumental coloration variable ...................................................................................... 3
—. Scape along its length and supraclypeal area with numerous, minute, erect to suberect bristles (Fig. 3); all metasomal terga with dense, long, fine, erect, simple, yellow setae intermixed with similar short, appressed to decumbent setae (Fig. 9); integument wholly yellow orange to orange (Figs. 7–9) .......................... ................................................................................................ Dasytrigona, n. subgen.
3(2). Discs of metasomal terga III–V with abundant, prominent, erect to subdecumbent, bristles, such bristles frequently, but not universally, arising amid dense tomentum .................................................................................................................... 4
—. Discs of metasomal terga III–V without bristles, instead with only fine, short to minute setae, such setae typically appressed to decumbent, if bristles present, then short (less than one-half ocellar diameter) and confined to lateral margins or rarely sparse over disc and not associated with tomentum ............ 6
4(3). Metasomal terga III–V not covered in yellow tomentum, at most with diffuse areas of whitish or yellowish tomentum laterally on discs of terga IV–VI (e.g., Fig. 2) [care should be taken as sometimes the tomentum is difficult to see or may be largely rubbed off and only present in small lateral areas or under the margin of the preceding tergum] ............................................................................. 5
—. Metasomal terga III–V covered with dense, yellow, plumose tomentum, typically obscuring integument (Fig. 1) [except in S. faviziae Engel tomentum interrupted broadly medially, and largely missing on tergum III] ................................ ............................................................................................ Scaptotrigona Moure, s.str.
5(4). Face below tangent of antennal toruli with a large vitreous yellow, yellowish brown, yellow patch (Figs. 37, 38, 40), clypeus not concolorous with frons; upper frons with minute punctures well-spaced, separated by 1–2× a puncture width ...................................................................................... Baryorygma, n. subgen.
—. Face below tangent of antennal toruli brown to dark brown, largely concolorous with remainder of head (Fig. 14), clypeus brown or concolorous with frons; upper frons with minute punctures dense, separated by much less than a puncture width, nearly contiguous in some places ............ Eoscaptotrigona, n. subgen.
6(3). Metasomal terga III–V finely imbricate, somewhat shining, with scatered punctures; mesoscutellum short, broadly rounded apically, apex extending only to basal margin of propodeum, not overhanging propodeum (Fig. 11) .. .............................................................................................. Astegotrigona, n. subgen.
—. Metasomal terga III–V coarsely imbricate to densely punctate; mesoscutellum long, apex somewhat blunt medioapically, apex extending well past basal margin of propodeum and thus overhanging propodeum (Fig. 10) ............................ ............................................................................................. Gymnotrigona, n. subgen.
description: Published as part of Engel, Michael S., 2022, Notes on South American stingless bees of the genus Scaptotrigona (Hymenoptera: Apidae), Part III: A revised infrageneric classification and new species, pp. 1-29 in Journal of Melittology 2022 (111) on pages 2-5, DOI: 10.17161/jom.i111.17013, http://zenodo.org/record/8057613