Aethemelikertes Engel, 2021

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 : 11-14

Aethemelikertes Engel , new genus

ZooBank: urn:lsid:zoobank.org:act:3BE946D0-89C7-4E2F-B82E-C733789DB6D1

TYPE SPECIES: Aethemelikertes emunctorii Engel, new species .

DIAGNOSIS: This genus is immediately recognizable for the inverted clypeal basin that projects over the clypeal disc as a broadly concave surface, laterally demarcated by carinae that extend to the clypeal apical margin ( Figs. 9–12 , 14, 16 ). In addition, the labrum is trapezoidal with lateral margins converging apically, the slope in the apical half different from that proximally, laterally without a fringe of prominent setae, and the blunt apical margin with a shallow medial concavity.

DESCRIPTION: ⚲: Small bee, ca. 3.9 mm in length; head wider than long, upper interorbital distance greater than compound eye length. Mandible with outer mandibular grooves reduced, faint impression of outer groove obliquely across apical half of mandible, vanishing well before apex; shallow indentation for single blunt preapical tooth along upper third of apical margin; axes of mandibular articulations converging anteriorly such that closed mandibles overlap at slightly obtuse angle and do not obscure or limit forward movement of labrum; malar space linear; labrum flat, slightly broader than medial length, lateral margins converging apically, with abrupt change in slope of convergence at about midlength, apical margin blunt, giving overall inverted trapezoidal appearance, apical margin with broad shallow concavity medially, surface with sparsely scatered suberect to erect setae, lateral margins without fringe of setae; clypeus with prominent basal modification, forming inverted basin overhanding clypeal disc, lateral margins of clypeal basin extending as longitudinal lateral carinae terminating at apical margin at juncture with labral basal angles; clypeal basin extending upward over supraclypeal area and between antennal toruli, as broad as intertorular space, upper apical margin seemingly slightly wavy or scalloped; disc of clypeus comparatively flat; epistomal sulcus laterally forming obtuse angle, medially sulcus obscured from view by clypeal basin; upper torular tangent slightly below head midlength; intertorular distance about 2× torular diameter; scape shorter than torulocellar distance; first flagellomere slightly longer than wide, longer than second flagellomere, second and third flagellomeres equal in length, each wider than long; ocelli high on vertex, situated well above upper tangent of compound eyes; vertex unmodified (no depressions or ridges); preoccipital area rounded; gena slightly narrower than compound eye in profile. Mesoscutum with anterior border low, broadly rounded; tegula elongate-ovoid; mesoscutellum low, rounded, not greatly projecting over metanotum and base of propodeum; propodeum with sloping basal area distinct from vertical posterior surface. Forewing with prominent, subtriangular pterostigma, pterostigma about 3× as long as maximum width, maximum width at about midlength, margin inside marginal cell sloping to costal margin; marginal cell acutely rounded apically, not appendiculate, apex offset from costal margin by about vein width; basal vein straight, confluent to overlapping slightly basad with 1cu-a; three submarginal cells present (1rs-m present), second submarginal cell trapezoidal, anterior border (3Rs) significantly shorter than r-rs, r-rs arising at about pterostigmal midlength (widest point); third submarginal cell broadest, but not broader than combined breadth of first and second submarginal cells; 1rs-m faintly arched, 2rs-m strongly arched, thus anterior border of third submarginal cell significantly shorter than posterior border of same cell; 1m-cu angulate at its extreme apex near second submarginal cell, entering second submarginal cell near cell midlength; anterior margin of hind wing with six distal hamuli arranged in an evenly spaced series; wing membranes hyaline clear; veins dark brown. Metatibia slender, elongate, length about 3.8× maximum width, posterior margin gently convex and slightly widening in apical two-thirds; surface of corbicula not depressed; posterior margin with fringe of elongate, plumose (branches minute and along length of setal rachis) setae, such setae as long as or longer than metatibial width, anterior margin with sparsely scatered simple setae and bristles, corbicular surface with sparsely scatered, erect, fine, simple setae, such setae long but not as long as those of posterior fringe; inner surface with keirotrichiate zone field covering most of surface except posterior, narrow, slightly depressed (i.e., a weak clivulus present) glabrate zone and a broad, squarish apical glabrate zone (sensu Rasmussen et al., 2017), apical glabrate zone slightly longer than apical width of metatibia; rastellum composed of stiff bristles along entire inner apical width of metatibia; single metatibial spur present, spur minutely ciliate along inner margin in apical half; metabasitarsus with auricle present on proximal surface facing apex of metatibia; metabasitarsus rectangular, longer than wide, length about 1.6× maximum width, margins roughly parallel, apical margin comparatively straight (i.e., posterior angle not projecting), inner surface with abundant, elongate, suberect, simple bristles; pretarsal claws with minute inner subapical ramus; arolium present. Metasoma broad, ovoid, sparsely setose and largely smooth and shining, most setae minute, simple, and appressed to subappressed, more numerous (but still sparse) on more apical terga; metasomal sterna unmodified, with scatered, short, erect, fine, simple setae in apical quarter to third of sterna II– IV; sting present.

ETYMOLOGY: The new genus-group name is a combination of the Greek aḗthēs (ἀήΘης), meaning, “unusual,” and Melikertes Engel [itself a combination of méli (μέλῐ, “honey”), keírô (κείρω, “to cut”), and – tḗs (– τής, appended to verbs to form agent nouns; in the present case, making “honey cuter”)], type genus of the tribe. The gender of the name is masculine.

Figures

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.

Figure 11. X-ray µCT scan of holotype worker of Aethemelikertes emunctorii, new genus and species (SMF Be 14262a), lateral view. Note that scan resolution was insufficient to resolve most setae.

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 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.