Melikertini

Engel, Michael S. & Davis, Steven R., 2021, New genera of melikertine bees with facial modifications in Baltic amber (Hymenoptera: Apidae), Journal of Melittology 2021 (103), pp. 1-52 : 10-11

Key to Genera of Melikertini

(modified and expanded from that of Engel, 2001 a, and Engel et al., 2014)

As noted by Engel et al. (2014) it remains unknown to what degree some of the characters presented here are gender or caste specific. Accordingly, care should be taken when using the key in relation to new material of hitherto unknown castes or sexes.

1. Disc of clypeus comparatively flat, without distinct lateral carinae and without bell-like concavity ...................................................................................................... 2

—. Clypeus with lateral carinae rising from apex to form margins of bell-like concavity arising from base of clypeus and overhanging disc ( Figs. 10 , 12 , 14, 16 ) .. ....................................................................................... Aethemelikertes Engel, n. gen.

2(1). Clypeal protrusion present, i.e., base of clypeus produced into variously modified facial prominences, prominence bending upward over fronto-clypeal portion of epistomal sulcus and obscuring supraclypeal area or even lowermost frons in facial view ( Figs. 3, 4 , 6 , 23–26 ) ................................................................... 3

—. Clypeal protrusion absent ......................................................................................... 4

3(2). Apex of clypeal protrusion narrow, narrower than intertorular distance ( Figs. 3, 4 , 6 ) ................................................................................................. Succinapis Engel

—. Apex of clypeal protrusion broad, as wide as or slightly wider than intertorular distance ( Figs. 23–26 ) ................................................. Haidomelikertes Engel, n. gen.

4(2). Mesoscutellum without tongue-like medioapical extension [females: workers] ....................................................................................................................................... 5

—. Mesoscutellum with prominent, tongue-like medioapical extension projecting over metanotum, propodeum, and portions of metasoma, dorsal surface of extension densely setose [males: drones] ...................... Mochlomelikertes Engel et al.

5(4). Mesoscutellum bulging, overhanging metanotum and propodeum; apical margins of metasomal terga distinctly lighter than remainder of metasoma, thus metasoma appears banded; anterior and posterior margins of metabasitarus distinctly converging toward apex .......................................................................... 6

—. Mesoscutellum not bulging, not overhanging metanotum or propodeum; metasomal terga uniformly colored; anterior and posterior margins of metabasitarsus approximately parallel ........................................................................................ 7

6(5). Forewing with anterior margin of first submarginal cell approximately equal to length of anterior margin of second submarginal (i.e., r-rs as long as immediately succeeding abscissa of Rs); compound eyes converging below; second flagellomere distinctly shorter than third flagellomere, first flagellomere distinctly shorter than combined lengths of second and third flagellomeres ............. .............................................................................................................. Melissites Engel

—. Forewing with anterior margin of first submarginal cell many times longer than length of anterior margin of second submarginal cell (i.e., r-rs many times longer than immediately succeeding abscissa of Rs); compound eyes approximately parallel; second and third flagellomeres approximately equal in length, first flagellomere approximately equal to combined lengths of second and third flagellomeres .............................................................................. Roussyana Manning

7(5). Apical margin of clypeus straight, flat, not flared anteriorly and not projecting over plane of labrum (genus Melikertes Engel, s.l.) ................................................. 8

—. Apical margin of clypeus flared and projecting anteriorly over plane with labrum, medioapically with shallow U-shaped emargination ( Figs. 34–36, 38, 39 , 57, 58, 60–62 ) ................................................................... Amelikertotes Engel, n. gen.

8(7). Forewing with two submarginal cells (1rs-m absent) .............................................. ......................................................................... Paramelikertes Engel & Ortega-Blanco

—. Forewing with three submarginal cells (1rs-m present) .... Melikertes Engel, s.str.

Figures

Figure 12. Ventral facial view of holotype worker of Aethemelikertes emunctorii, new genus and species (SMF Be 14262a). Note carinae demarcating lateral margins of basin extending to clypeal apex where clypeus extends laterally around base of labrum.

Figures 9–10. Holotype worker of Aethemelikertes emunctorii, new genus and species, in Eocene (Bartonian) Baltic amber (SMF Be 14262a). 9. Ventral view. 10. Slightly obliquely dorsal facial view emphasizing upper, slightly scalloped margin of clypeal basin.

Figures 13–16. X-ray µCT scans of heads of holotype workers of Succinapis micheneri Engel (AMNH B-JH103) and Aethemelikertes emunctorii, new genus and species (SMF (Be 14262a), in Baltic amber; yellow highlights disc and modification of clypeus, orange highlights labrum. 13. Facial view of S. micheneri. 14. Facial view of A. emunctorii. 15. Oblique profile of S. micheneri. 16. Oblique profile of A. emunctorii. Note that scan resolution was insufficient to resolve most setae.

Figures 3–5. Worker of Succinapis micheneri Engel (SEMC B-018). 3. Facial view. 4. Dorsal view of head and mesoscutum. 5. Right lateral view.

Figures 6–8. Worker of Succinapis micheneri Engel (SEMC B-017). 6. Oblique facial view. 7. Outer (prolateral) view of metatibia and metabasitarsus. 8. Detail of fringe setae of metatibial posterior/upper margin; white arrow indicates a deceptive internal microfracture of resin trail with branched fractal patern (such fracture planes and trails are a common taphonomic structure among or even running alongside many fine setae in amber inclusions, and can give such setae an artificially plumose appearance; accordingly, care must be taken before concluding whether or not amber-included setae are branched); black arrow highlights one of many truly plumose setae, separate from the internal microfracture planes.

Figures 23–26. X-ray µCT scans of heads of holotype workers of Haidomelikertes proboscidea (Engel), new combination (AMNH B-JH96), and H. uraeus, new genus and species (SMF (Be 14263a), in Baltic amber; yellow highlights disc and modification of clypeus, orange highlights labrum. 23. Facial view of H. proboscidea. 24. Facial view of H. uraeus. 25. Oblique profile of H. proboscidea. 26. Oblique profile of H. uraeus. Note that scan resolution was insufficient to resolve most setae.

Figures 34–39. PPC-SRµCT scan of worker head of Amelikertotes clypeata (Engel), new combination; upper right worker from figure 29. 34. Dorsal view. 35. Ventral view. 36. Facial view. 37. Posterior view. 37. Right lateral view. 38. Left lateral view. Arrows point to flared and cleft clypeus. Note that scan resolution was insufficient to resolve most fine setae.

Figures 57–62. PPC-SRµCT scan of worker head of Amelikertotes clypeata (Engel), new combination; lower left worker from figure 29. 57. Facial view. 58. Right lateral view. 59. Posterior view. 60. Left lateral view. 61. Ventral view. 62. Ventral view with mandibles removed to reveal labrum. Scale bar in center for 57–60, scale bar at botom left for 61 and 62. Note that scan resolution was insufficient to resolve most fine setae.