Plebeia

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 : 69-71

Key to Genera and Subgenera of Plebeia Genus Group

(worker caste; partly emended and expanded from Silveira et al., 2002; Michener, 2007)

1. Prolateral surface of metatibia flat or concave apically, forming corbicula, proventral margin gently convex to concave, differing from retromarginal contour; penicillum present; rastellum variable; first flagellomere shorter than combined lengths of second and third flagellomeres .............................................................. 2

—. Prolateral surface of metatibia convex, without corbicula, proventral margin convex like retromarginal contour; penicillum absent; rastellum consisting of tapering setae; first flagellomere nearly as long as combined lengths of second and third flagellomeres ................................................................ Lestrimelita Friese

2(1). Anterior margin of mesoscutellum with shining, longitudinal, V- or U-shaped median depression opening anteriorly into mesoscutal-mesoscutellar fossa; posterior margin of mesoscutellum notched or emarginate medially; preoccipital carina present, extending far down each side of head; integument of head and mesosoma, or at least mesoscutellum, with coarse, cribriform punctation [Genus Nannotrigona Cockerell , s.l.] ......................................................................... 3

—. Anterior margin of mesoscutellum without shining, longitudinal, median depression; posterior margin of mesoscutellum entire; preoccipital carina absent or weakly indicated only by transverse dorsal section posterior to vertex; integument of head and mesosoma with fine, often scatered, punctation .......... 4

3(2). Mesoscutum and mesoscutellum with dense, coarse, cribriform punctures ( Fig. 122 ); larger bees, head width more than 1.6 mm .... Nannotrigona Cockerell , s.str.

—. Mesoscutum sparsely punctate, integument between punctures shining, contrasting denser, coarser punctation of mesoscutellum ( Fig. 123 ); smaller bees, head width less than 1.6 mm ............. Lispotrigona Gonzalez & Engel , n. subgen.

4(2). Retrolateral surface of metatibia with strongly depressed superior glabrate zone, superior glabrate zone at least apically about as broad as keirotrichiate zone .............................................................................................................................. 5

—. Retrolateral surface of metatibia with depressed superior glabrate zone narrow, much less than half as wide as keirotrichiate zone, or absent, keirotrichia extending to or close to margin ................................................................................ 8

5(4). Retrolateral surface of metabasitarsus without basal sericeous area ................. 6

—. Retrolateral surface of metabasitarsus with basal sericeous area .......................... ........................................................................................................ Tetragonisca Moure

6(5). Compound eyes bare; rastellum strongly developed ........................................... 7

—. Compound eyes setose; rastellum reduced to tapering setae ................................ ................................................................................. Trichotrigona Camargo & Moure

7(6). Posterior margin of vertex elevated as strong, setose ridge between summits of compound eyes; superior distal angle of metatibia acute .......... Duckeola Moure

—. Posterior margin of vertex not elevated; superior distal angle of metatibia broadly rounded ...................................................................... Frieseomelita Ihering

8(4). Metabasitarsus thickened, prolateral surface swollen, nearly as broad as or broader than metatibia, bristles of inferior retrolateral margin curved apically; yellow maculation absent; rastellum nearly occupying full length of metatibial apical margin [Genus Scaura Schwarz , s.l.] ............................................................. 9

—. Metabasitarsus not thickened, prolateral surface flat, much narrower than metatibia; bristles of inferior retrolateral margin straight; yellow maculation present; rastellum occupying two-thirds or less of metatibial apical margin ...... ..................................................................................................................................... 10

9(8). Metabasitarsus as wide as or wider than metatibia; malar space shorter than flagellar diameter; gena in profile narrower than compound eye; mandible virtually edentate .......................................................................... Scaura Schwarz , s.str.

—. Metabasitarsus narrower than metatibia; malar space as long as flagellar diameter; gena in profile broader than compound eye; mandible with two denticles .. .......................................................................................................... Schwarzula Moure

10(8). Head and mesosoma largely smooth and shining between scatered small setiferous punctures, rarely granulose-microrugulose and more mate; mesepisternum with at least some simple erect setae among plumose setae ..................... 11

—. Head and mesosoma with large, dense punctation or integument mate and microreticulate with indistinct punctures; mesepisternum with erect setae always plumose or minutely branched .............................................................................. 14

11(10). Clypeo-ocular distance at base of clypeus 2× torular diameter or less; scape distinctly shorter than torulocellar distance; metatibia shorter, length 2.2–2.5× maximum width, with apical proventral margin comparatively straight; mesoscutellum width about 2× medial length; r-rs 0.5× length Rs+M or frequently less; malar space less than 0.5× flagellar diameter, often linear; smaller bees ..... ..................................................................................................................................... 12

—. Clypeo-ocular distance at base of clypeus 2.5× torular diameter or more; scape as long as or slightly longer than torulocellar distance; metatibia long, length 2.6–2.8× maximum width, with apical proventral margin curved; mesoscutellum width about 1.9× medial length; r-rs 0.6× length or more of Rs+M; malar space 0.25–0.65× flagellar diameter; larger bees ........................ Plectoplebeia Melo

12(11). Mesoscutum generally mate owing to finely microrugulose-granulose sculpture resulting from dense, coarse, shallow punctures ( Figs. 124, 125 ) ................... ............................................................................................. Asperplebeia Engel, n. gen.

—. Mesoscutum shining and smooth, punctures small to minute and distinctly separated, often widely so ( Figs. 126, 127 ) [Genus Plebeia Schwarz , s.l.] ........... 13

13(12). Forewing 2Cu a faint nebulous trace, weakening apically and disappearing by wing margin; minute bees, 2–3.5 mm in length ..... Nanoplebeia Engel , n. subgen.

—. Forewing 2Cu terminating on wing margin as a dark brown to brown tubular vein or nebulous trace, no weaker at terminus than on remigium; small bees, typically 3.5 mm or greater in length .................................... Plebeia Schwarz , s.str.

14(10). Head and mesosoma with conspicuous yellow maculation; erect sternal setae predominantly plumose; moderate-sized bees, body length over 5 mm [Genus Schwarziana Moure , s.l.] ........................................................................................... 15

—. Head and mesosoma with exceptionally small areas of yellow maculation; erect sternal setae simple; smaller bees, body length less than 4 mm ... Friesella Moure

15(14). Integument without metallic reflections; mesoscutum mate, integument microreticulate, with punctures indistinct ................................................................ 16

—. Integument with weak metallic reflections; mesoscutum shining, punctures distinct and dense ............................................................................... Mourella Schwarz

16(15). Malar space shorter than flagellar diameter; mesepisternal setae long, longer than protibial width, and dense, sometimes obscuring integument ..................... .............................................................................................. Schwarziana Moure , s.str.

—. Malar space as long as flagellar diameter; mesepisternal setae short, shorter than protibial width, and sparser .............................. Chapadapis Engel , n. subgen.

Figures

Figures 122–123. Mesosomal dorsum of workers of Nannotrigona Cockerell. 122. Nannotrigona (Nannotrigona) perilampoides (Cresson). 123. N. (Lispotrigona) schultei (Friese).

Figures 124–127. Mesosomal dorsa of workers of Asperplebeia, new genus, and Plebeia Schwarz. 124. Mesosomal dorsum of Asperplebeia moureana (Ayala), new combination. 125. Detail of mesoscutal disc of A. moureana. 126. Mesosomal dorsum of Plebeia (Nanoplebeia) minima (Gribodo). 127. Detail of mesoscutal disc of P. (N.) minima.