Scaptotrigona (Gymnotrigona) nuda, 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 : 20-22

Scaptotrigona (Gymnotrigona) nuda Engel, new species

ZooBank: urn:lsid:zoobank.org:act:587185D9-98D2-464F-BC1B-6E0A71A4023E

( Figs. 33, 34 )

DIAGNOSIS: This species belongs to a small group of species in Gymnotrigona lacking minute fimbriae on the metasomal terga. Among these, S. nuda could be most easily confused for S. jujuyensis (Schrotky) , which occurs further to the South and Southeast in northern Argentina. It can be most readily distinguished from this species by the longer bristles on the mesoscutum (vide Key, supra), and from S. guiamaraesensis Laroca & Almeida by the darker facial coloration (cf. Figs. 32 , 34 ).

DESCRIPTION: As described for S. totobi (vide supra) except as follows: ⚲: Total body length approximately 5.9 mm, forewing length (to base of humeral sclerite) 5.7 mm. Head wider than long, width 2.45 mm, length 1.97 mm; compound eye length 1.45 mm; upper interorbital distance 1.61 mm, lower interorbital distance 1.48 mm. Scape length 0.94 mm, slightly longer than torulocellar distance, torulocellar distance 0.88 mm. Clypeus approximately 1.6× as wide as long, length 0.64 mm, width 1.03 mm. Malar area 1.6× flagellar diameter. Preoccipital carina strong, lamellate dorsally and bordered by deep medial and lateral indentations, carina interrupted laterally by deep concavity, preoccipital lamella extending slightly into concavity, lower margin of concavity projected upward as acute, lamellate tooth.

Integument generally black to dark brown; clypeus dark chestnut brown with apical margin black; supraclypeal area dark chestnut brown; face below tangent of antennal toruli dark chestnut brown along inner orbit, blending to faint yellow spot by clypeus and lower antennal torulus margin (resembling in this respect the facial markings of S. bipunctata ); malar space dark chestnut brown to dark brown; scape dark brown above, narrowly yellow brown to orange ventrally; flagellum dark brown except light brown to orange below; hypostomal borders yellow brown; wing membranes hyaline clear; veins orange.

Sculpturing as described for S. psile (vide supra).

Fine pubescence generally consisting of sparse, minute, appressed or decumbent white to fulvous setae, such minute setae often simple but sometimes plumose, intermixed in places with fuscous to black setae; minute white setae sparse on lower face, more numerous on frons except becoming more fulvous, blending to more erect fulvous to black setae on upper frons and vertex; gena with scatered white setae similar to that of face; postgena with longer, erect, fulvous setae. Pronotal lobe with dense, white, plumose setae; mesoscutum and mesoscutellum with scatered, minute, simple, subappressed to decumbent, fulvous setae; metanotum with abundant, white, plumose setae; mesepisternum with similar setae to that of mesoscutum, such setae blending ventrally to longer, white setae ventrally; metepisternum and lateral surface of propodeum with dense, white, plumose setae. Legs with largely black setae, except coxae, trochanters, and proximally on femora long, white to fuscous setae. Metasomal terga with sparse, minute, appressed, simple, fulvous setae, although such setae slightly longer and more numerous, albeit still sparse, on terga IV–VI; sterna with elongate, erect, off-white to lightly fuscous simple scopal setae, such setae with wavy apices. Bristles in distinct areas of body: upper frons and vertex with black bristles, those of vertex longest, particularly medially posterior to ocelli; black bristles along anterior margin of pronotal lobe; mesoscutum anterior and lateral margins with abundant black bristles; tegula with suberect black bristles anteriorly; mesoscutellum with black bristles abundant, longest along margin; black bristles scatered over mesepisternum and a distinct line of such bristles along rounded margin with preëpisternum; legs with numerous black bristles, those of distitarsomeres typically fulvous; metatibial and metabasitarsal bristles black, some with fulvous tips. Metasoma terga I–III without bristles; tergum IV typically without bristles but sometimes with one or two minute, subdecumbent, fulvous to black bristles laterally; tergum V with a few, minute, subdecumbent, fulvous to black bristles laterally; tergum VI with minute bristles sparse to absent on disc, and long, erect, fulvous or fuscous to black bristles laterally and along margin.

♀: Latet.

♂: Latet.

HOLOTYPE: ⚲, Bolivia: El Beni, Beni Stn., Palm Camp, Savannah , NE of San Borja, 28 July 1988, R. W. Brooks ( SEMC).

ETYMOLOGY: The specific epithet is taken from the Latin adjective nūdus, meaning, “unclothed”.

Figures

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.

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.