Gymnotrigona Engel, 2022

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, Journal of Melittology 2022 (111), pp. 1-29 : 11-13

Gymnotrigona Engel , new subgenus

ZooBank: urn:lsid:zoobank.org:act:8055F509-DEC5-4711-8862-1553268A0831

TYPE SPECIES: Trigona (Scaptotrigona) depilis Moure, 1942 .

DIAGNOSIS: Like Astegotrigona (vide infra), Gymnotrigona lacks prominent suberect bristles on the discs of metasomal terga III–V, although sometimes there are some minute (less than 0.5× ocellar diameter), subdecumbent bristles. It differs from Astegotrigona in that the mesoscutellum is blunt medially and comparatively long, with the apex extending beyond the basal margin of the propodeum, overhanging the basal third or more of the propodeum ( Fig. 10 ). Additionally, metasomal terga III–V are coarsely imbricate to densely punctate, and more mate. The integument is largely black, but with some vitreous to more well-defined facial markings on the lower face, although in one species the coloration is somewhat lighter overall ( S. stipula , vide infra) and in two there are extensive areas of orange ( Figs. 19–24 ). The subgenus occurs from Mexico to Argentina, but the species are few and not common.

ETYMOLOGY: The new name is a combination of the Ancient Greek adjective gumnós (γυμνός, meaning, “unclad”) and Trigona . The gender of the name is feminine.

Key to Species of Gymnotrigona

1. Head, mesosoma, and legs wholly or nearly entirely dark brown to black ( Figs. 30–36 ; bristles of vertex and mesoscutellum black ............................................... 2

—. Head, mesosoma, legs, and sometimes metasoma with extensive areas of orange, particularly either mesoscutum or mesoscutellum wholly orange ( Figs. 19–24 ); bristles of vertex and mesoscutellum yellow to fulvous ....................... 7

2(1). Apical margins of terga II–V or III–V with fine, minute fimbriae; metasomal terga II–IV with short, subdecumbent to suberect lateral bristles, or without bristles laterally on terga II and III, but a few bristles on terga IV and V ......... 3

—. Apical margins of terga II–V without fimbriae; metasomal terga II–IV without lateral bristles ...................................................................................................... 5

3(2). Metasomal terga II and III with minute, sparse, lateral bristles; genal tooth present as acute lamella projecting upward .......................................................... 4

—. Metasomal terga II and III without lateral bristles; genal tooth absent, lower margin of concavity rounded [ Venezuela] ...................................... S. psile , n. sp.

4(3). Sparse, minute, decumbent bristles of terga III and IV golden fulvous; mesoscutellum black to dark brown, sometimes with light brown apically; tergum VI without black bristles [ Brazil: Mato Grosso, Mato Grosso do Sul, Goiás, Santa Catarina, Paraná, Rio Grande do Sul; Argentina: Misiones ; Paraguay] ............................................................................................... S. depilis (Moure)

—. Sparse, minute, decumbent bristles of terga III and IV black; mesoscutellum brownish orange with yellow brown apically; tergum VI with minute, black bristles [ Brazil: São Paulo] ................................................. S. stipula , n. sp.

5(2). Bristles of mesoscutal anterior margin long, 0.15–0.30 mm .............................. 6

—. Bristles of mesoscutal anterior margin short, approximately 0.05–0.09 mm [ Argentina] ......................................................................... S. jujuyensis (Schrotky)

6(5) Clypeus dark chestnut brown, with apical margin black ( Fig. 31 ); face below level of antennal toruli with yellowish spots bordering upper half of clypeus and lower outer margin of antennal torulus, separated from inner orbits by dark chestnut brown ( Fig. 31 ); genal tooth present and large [ Bolivia] .... S. nuda , n. sp.

—. Clypeus largely yellow to brownish yellow ( Fig. 32 ); face below level of antennal toruli yellow to brownish yellow from inner orbit to clypeus, often extending along inner orbit as thin strip above level of antennal toruli by about a torular diameter ( Fig. 32 ); genal tooth absent to scarcely a short, rounded protuberance [ Brazil: Rondônia, Goiás, Mato Grosso] ... S. guiamaraesensis Laroca & Almeida

7(1). Mesoscutum largely orange, with thin longitudinal black stripes on either side of midline ( Fig. 10 ); mesoscutellum dark brown to black ( Fig. 10 ); tegula largely dark brown, lighter posteriorly ( Fig. 10 ); metasoma typically with extensive orange markings ( Fig. 19 ) [ Mexico] ........................... S. hellwegeri (Friese)

—. Mesoscutum black ( Fig. 21 ); mesoscutellum orange ( Fig. 21 ); tegula orange ( Fig. 21 ); metasoma without orange markings ( Figs. 20, 21 ) [ Venezuela] ........... ....................................................................................................... S. aurantipes , n. sp.

Figures

Figure 19. Lateral habitus of worker of Scaptotrigona (Gymnotrigona) hellwegeri (Friese).

Figures 20–22. Worker of Scaptotrigona (Gymnotrigona) aurantipes, new species. 20. Lateral habitus. 21. Dorsal habitus. 22. Facial view.

Figures 23–25. Drone of Scaptotrigona (Gymnotrigona) aurantipes, new species. 23. Lateral habitus. 24. Facial view. 25. Dorsal habitus.

Figures 10–11. Mesosomal dorsa of Scaptotrigona Moure. 10. Scaptotrigona (Gymnotrigona) hellwegeri (Friese). 11. S. (Astegotrigona) wheeleri (Cockerell).

Figures 30–32. Workers of Scaptotrigona Moure. 23. Lateral habitus of Scaptotrigona (Gymnotrigona) psile, new species. 31. Facial view of S. (G.) psile. 32. Facial view of S. (G.) guimaraesensis Laroca & Almeida.

Figures 33–36. Workers of Scaptotrigona Moure. 33. Lateral habitus of Scaptotrigona (Gymnotrigona) nuda, new species. 34. Facial view of S. (G.) nuda. 35. Facial view of S. (G.) stipula, new species. 36. Lateral habitus of S. (G.) stipula.