Tetragonula (Tetragonula) florilega, 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 : 25-33

Tetragonula (Tetragonula) florilega Engel, new species

ZooBank: urn:lsid:zoobank.org:act:E37B966D-89B6-4F39-8C2E-CF9EDDAEFB27

( Figs. 24–43 )

DIAGNOSIS: Tetragonula florilega intermingles traits of the last two informal species groups in the above key: the forewing length, including the tegula, is approximately 3.3 mm in most specimens, fiting the iridipennis -group, yet the mesoscutum is quite clearly evenly and finely setose ( Fig. 38 ), without any longitudinal glabrous bands as is otherwise present the laeviceps -group. In addition, the clypeus is apically marked with tawny to yellow coloration ( Figs. 27–30 ), and the mesoscutellum is sometimes tawny brown. As in most Tetragonula , the setae of the mesepisternum are distinctly sparser posteriorly ( Fig. 36 ), contrasting with the more numerous setae of the anterior portion as well as the metepisternum.

DESCRIPTION: ⚲: Total body length approximately 3.0–3.3 mm, forewing length (including tegula) 3.2–3.5 mm. Head wider than long, width 1.1–1.5 mm, length 1.12–1.15 mm; compound eye length 0.92–0.95 mm; upper interorbital distance 0.82–0.86, lower interorbital distance 0.58–0.63. Scape length 0.44–0.46 mm, shorter than torulocellar distance, torulocellar distance 0.63 mm. Clypeus broader than long, approximately 2× as wide as long, length 0.14–0.15 mm, width 0.28–0.30 mm. Malar space linear ( Figs. 24 , 27–30 , 32 ). Mandible with two, small preapical teeth ( Fig. 31 ), with narrow incision separating first preapical tooth (P 1) from apical edentate margin; incision separating P 1 and P 2 slightly less than orthogonal, with acutely rounded angular geometric vertex. Labrum transverse, surface gently convex, apical margin faintly and broadly convex. Labial palpomeres I and II with elongate straight to slightly wavy ventral setae ( Figs. 27 , 29, 30 ). Mesoscutellum comparatively thick and broadly rounded in profile, overhanging metanotum and base of propodeum; basal area of propodeum subequal or slightly shorter than mesoscutellum, steeply sloping to rounded angle with vertical posterior surface. Forewing extending beyond apex of metasoma, marginal cell narrowly open apically, with faint nebulous stub (appendiculate), stub not bent and without stub of 2r-rs at origin; 1M slightly offset proximad 1cu-a; M straight, 2M terminating bluntly at nebulous 1m-cu ( Fig. 37 ); hind wing with 5 distal hamuli ( Fig. 39 ), 1M distinctly bent proximally. Metatibia triangular, approximately 3× as long as greatest width; retromarginal contour slightly convex, with subangulate superior distal angle; corbicula shallowly concave, occupying distal third of prolateral surface ( Fig. 40 ); keirotrichiate zone of retrolateral surface separated from supraglabrate zone by steep clivulus. Metabasitarsus with proventral margin straight, retrodorsal margin gently convex; superior distal angle not projecting ( Figs. 33, 34 , 40, 41 ); retrolateral surface with prominent basal sericeous area ( Fig. 41 ). Metasoma short, subequal to head width, widest second and third segments, remaining terga progressively narrower.

Integument generally black to dark brown (silvery reflective surfaces on some specimens result from microscopic separation of integument from amber matrix; separation produces microscopic reflective air spaces that appear silvery, particularly under strong reflective lighting); mouthparts pale brown; mandible largely tawny to yellow, with black apical margin ( Figs. 29–31 ); labrum brown to tawny; clypeus largely black except apically tawny to yellow (in finest preserved specimens clypeus is apically yellow, progressing to a more brownish appearance in less well preserved individuals) ( Figs. 24 , 27–29 ); scape light brown to tawny, slightly darker dorsally ( Figs. 25 , 27 , 28 , 30 ), flagellum dark brown; remainder of head black. Mesosoma black, pronotum brown, pronotal lobe often light brown ( Fig. 28 ); tegula light brown, sometimes appearing slightly semi-translucent; mesoscutellum black ( Figs. 35, 38 ) to partly tawny brown with black or dark brown on axillae and anterior of mesoscutellum in some individuals ( Fig. 26 ). Wing membranes hyaline clear ( Figs. 24, 26 , 37 ); tubular veins dark brown to brown, pterostigma lighter centrally, nebulous veins brown to light brown. Legs largely black to dark brown, slightly lighter on pro- and mesotarsi. Metasoma dark brown to black.

Integument mostly smooth and shining, with scatered, faint, shallow, minute punctures; clypeus with minute punctures separated by 1–2× a puncture width, face with faint minute punctures sparser, separated by 2.5–5× a puncture width, punctures of gena as on face, postgena apparently impunctate and faintly imbricate. Mesosoma largely smooth and shining; mesoscutum and mesoscutellum with sparse, faint, shallow, minute punctures; tegula finely and faintly imbricate; mesepisternum apparently impunctate; basal area of propodeum smooth, polished. Metasomal terga smooth, impunctate; sterna faintly imbricate.

Pubescence largely decumbent and pale. Labrum with sparse, minute, simple setae except apically setae longer; face with abundant, fine, decumbent, minute, simple setae, not obscuring integument ( Figs. 24 , 28 , 30 ), such setae on lower two thirds to one half of face minutely plumose, particularly around antennal toruli; setae of vertex and ocellocular area longer and erect; setae of gena like those of face; postgena with scatered, erect, simple setae. Mesoscutum with scatered, fine, erect, short, simple, such setae abundant but not obscuring integument, uniformly distributed (i.e., not organized into linear bands with longitudinal glabrous interspaces) ( Figs. 35, 38 ); mesoscutellum with setation as on mesoscutellum except some setae slightly longer ( Fig. 38 ), particularly posteriorly; mesepisternum with decumbent, fine, minutely plumose setae anteriorly, posteriorly largely glabrous ( Fig. 36 ), with some fine, simple setae largely ventrally; metepisternum and lateral surface of propodeum with setae like anterior half of mesepisternum, albeit those of propodeum not as numerous as those of metepisternum. Wing membrane with scatered microtrichia, area beneath costal notch with microtrichia; microtrichia along forewing apical margin absent. Metatibia with scatered, long, erect, simple setae on proventral surface, retromarginal fringe almost entirely composed of long (although not as long as setae of proventral surface), plmuose setae ( Figs. 40–42 ); setae on fundus largely short, subappressed to suberect, fine, largely simple setae ( Fig. 40 ); remainder of prolateral surface including corbicula sparse, elongate, erect to suberect, simple setae; penicillum composed of fine waxy setae ( Fig. 40 ), rastellum composed of semi-soft setae ( Fig. 41 ); retrolateral surface of metatibia with keirotrichiate zone ooccupying majority of surface, broader than supraglabrate zone, apical with about as long as apicoglabrate zone ( Fig. 41 ); prolateral surface of metabasitarsus with pollen pocket, ridge for fine fimbriate line exceedingly weak, prolateral surface otherwise with scatered, sparse, short, erect, simple setae; proventral surface with scatered elongate, suberect setae; retrodorsal margin with a few short setae; retrolateral surface of metabasitarsus with elongate, apically direct- ed, simple bristles forming rough setal ctenidia ( Fig. 41 ), apically last row forming apical bristle comb projecting beyond metabasitarsal apex. Metasomal terga largely glabrous, with exceptionally sparse minute, appressed, fine, simple setae largely present laterally, and with similar minute, appressed, apically directed, fine, simple setae scatered apically and subapically, discs with exceedingly sparse, short, erect, simple setae; terga V and VI with erect discal setae seemingly slightly less sparse than preceding terga and with suberect, apically directed, short setae apically; metasomal sterna with long, erect, simple setae.

♀: Latet.

♂: Latet.

HOLOTYPE: ⚲, NIGP 176093 ; deposited in the Nanjing Institute of Geology and Palaeontology , Chinese Academy of Sciences, Nanjing, China.

PARATYPES (47⚲⚲): 1⚲ (with pollen in corbicula), NIGP 176094 ; 1⚲, NIGP 176095 ; 1⚲, NIGP 176096 ; 1⚲, NIGP 176097 ; 1⚲, NIGP 176098 ; 1⚲, NIGP 176099 ; 1⚲, NIGP 176100 ; 1⚲, NIGP 176101 ; 1⚲, NIGP 176102 ; 1⚲, NIGP 176103 ; 1⚲, NIGP 176104 ; 1⚲, NIGP 176105 ; 1⚲, NIGP 176106 ; 1⚲, NIGP 176107 ; 1⚲, NIGP 176108 ; 1⚲, NIGP 176109 ; 1⚲, NIGP 176110 ; 1⚲, NIGP 176111 ; 1⚲, NIGP 176112 ; 1⚲, NIGP 176113 ; 1⚲, NIGP 176114 ; 1⚲, NIGP 176115 ; 1⚲, NIGP 176116 ; 1⚲, NIGP 176117 ; 1⚲, NIGP 176118 ; 1⚲, NIGP 176119 ; 1⚲, NIGP 176120 ; 1⚲, NIGP 176121 ; 1⚲, NIGP 176122 ; 1⚲, NIGP 176123 ; 1⚲, NIGP 176124 ; 1⚲, NIGP 176125 ; 1⚲, NIGP 176126 ; 1⚲, NIGP 176127 ; 5⚲⚲, NIGP 176128 ; 3⚲⚲ (tightly clustered together), NIGP 176129 , same locality and repository as holotype; 1 ⚲, SEMC F002514 ; 1⚲, SEMC F002515 ; 2⚲⚲, SEMC F002516 , in Division of Entomology , University of Kansas Natural History Museum; 1 ⚲, AMNH Zh-001, in Division of Invertebrate Zoölogy, American Museum of Natural History .

ATTRIBUTED NON-TYPE MATERIAL (37⚲⚲): 1⚲, NIGP 176060 ; 1⚲, NIGP 176061 ; 1⚲, NIGP 176062 ; 1⚲, NIGP 176063 ; 1⚲, NIGP 176064 ; 1⚲, NIGP 176065 ; 1⚲, NIGP 176066 ; 1⚲, NIGP 176067 ; 1⚲, NIGP 176068 ; 1⚲ (partial), NIGP 176069 ; 1⚲ (partial), NIGP 176070 ; 1⚲, NIGP 176071 ; 1⚲, NIGP 176072 ; 3⚲⚲, NIGP 176073 ; 1⚲, NIGP 176074 ; 1⚲, NIGP 176075 ; 1⚲, NIGP 176076 ; 3⚲⚲, NIGP 176077 ; 1⚲, NIGP 176078 ; 1⚲, NIGP 176079 ; 1⚲, NIGP 176080 ; 1⚲, NIGP 176081 ; 1⚲, NIGP 176082 ; 1⚲, NIGP 176083 ; 1⚲, NIGP 176084 ; 1⚲ (head only), NIGP 176085 ; 1⚲, NIGP 176086 ; 1⚲, NIGP 176087 ; 1⚲, NIGP 176088 ; 1⚲, NIGP 176089 ; 1⚲, NIGP 176090 ; 1⚲, NIGP 176091 ; 1⚲, NIGP 176092 ; same locality and repository as holotype .

TYPE LOCALITY: Zhangpu County, Zhangzhou Prefecture, Fujian Province, China.

HORIZON: Middle Miocene: Langhian, 14.7 Ma; sedimentary layer II, Fotan Group.

ETYMOLOGY: The specific epithet is taken from the Latin florilegus, meaning, “flower-gathering.”

COMMENTS: It was initially believed that those individuals with a more tawny brown mesoscutellum represented a separate distinct species of Tetragonula . However, no further differences could be identified among the series of specimens available and so it was considered merely a variation. As more material becomes available in the future, correlations between differences in the degree of tawny brown to yellow on the clypeus (those with yellow have a larger part of the clypeal apex colored versus those with more tawny or brown colors, although the later almost universally have the integument seemingly more augmented by preservation) and that of tawny color on the mesoscutellum to see if these are associated with morphometric distinctions, suggesting two cryptic species in the Zhangpu biota.

Figures

Figure 27. Left frontolateral oblique view of worker (SEMC F002514) of Tetragonula (Tetragonula) florilega, new species. Note elongate ventral setae of labial palpomeres I and II.

Figure 28. Oblique facial view of worker (NIGP 176110) of Tetragonula (Tetragonula) florilega, new species. Note yellowish apical two-fifths of clypeus.

Figures 29–31. Facial view and mouthpart structures of worker (SEMC F002515) of Tetragonula (Tetragonula) florilega, new species. 29. Detail of labrum, mandibles, apical portions of labial palpomeres, portions of antennae, and glossa. 30. Facial view. 31. Detail of dentition of left mandible (P 1 and P 2 = first and second preapical teeth).

Figures 24–26. Photographs of workers of Tetragonula (Tetragonula) florilega, new species, in mid- Miocene amber from Zhangpu, China. 24. Right frontal oblique habitus of SEMC F002514. 25. Right lateral habitus of NIGP 176108. 26. Dorsal habitus of NIGP 176122.

Figures 32–34. Worker (NIGP 176093) of Tetragonula (Tetragonula) florilega, new species, µCT scans. 32. Facial view. 33. Prolateral view of metatibia and metatarsus. 34. Retrolateral view of metatibia and metatarsus.

Figures 35–39. Workers of Tetragonula (Tetragonula) florilega, new species. 35. Dorsal view of head and oblique dorsal view of mesosoma (NIGP 176093). 36. Mesosoma in profile, with arrow indicating largely bare posterior surface of mesepisternum relative to the more abundant, appressed, white, plumose setae of the anterior portion (AMNH Zh-001). 37. Wing venation (SEMC F002514). 38. Oblique dorsal view of mesosoma, noting uniform setation (NIGP 176124). 39. Expanded detail of leading edge of hind wing showing distal hamuli (SEMC F002514).

Figures 40–42. Leg details of workers of Tetragonula (Tetragonula) florilega, new species. 40. Prolateral view of metatibia and metabasitarsus (NIGP 176111). 41. Retrolateral view of metatibia and metatarsus (NIGP 176118). 42. Detail of plumose retromarginal setal fringe along metatibia (NIGP 176111).

Figures 43–44. Lateral habitus µCT scans of workers of Zhangpu stingless bees. 43. Tetragonula (Tetragonula) florilega, new species (NIGP 176093). 44. Austroplebeia (Anteplebeina) fujianica, new subgenus and species (holotype, NIGP 176057). Note differences in malar spaces, metatibiae, and mesoscutella + propodea.