Haidomelikertes 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 : 19-22

Haidomelikertes Engel , new genus

ZooBank: urn:lsid:zoobank.org:act:8C4FFC1B-AD66-431C-96DD-96AA7A98CC6C

TYPE SPECIES: Haidomelikertes uraeus Engel, new species.

DIAGNOSIS: This genus includes those species with broad clypeal basal protrusions that are as wide as the intertorular distance and therefore completely cover the entire supraclypeal area in facial view ( Figs. 23–26 ) (when viewed from above the clypeal protrusion fills the entire intertorular space, versus being distinctly narrower, typically about one half, the intertorular space in Succinapis ). The clypeal protrusion in Haidomelikertes superficially resembles a rearing cobra, and does not form an inverted convex basin with lateral carinae as is present in Aethemelikertes (vide supra). In addition, the labrum is subtriangular, with a prominent lateral fringe of stiff, erect, elongate setae arising from the labral surface ( Fig. 28 ); the apical margin is narrowly blunt and not concave medially; and the convergence of the lateral margins does not change slope at midlength (contrast with that of Aethemelikertes , supra). Lastly, the apical glabrate zone on the inner surface of the metatibia is shorter than the apical metatibial width ( Fig. 19 ) (versus longer in Aethemelikertes ).

DESCRIPTION: ⚲: Small bees, ca. 3.3–4.2 mm in length; head as wide as or slight 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 to upper quarter 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, without change in slope of convergence, apical margin narrowly blunt, therefore surface of inverted trapezoidal shape, surface with sparsely scatered suberect to erect short setae, laterally with fringe of stiff, elongate, erect setae; clypeus with prominent, broad basal protrusion dorsally extending over supraclypeal area and between antennal toruli, as broad as intertorular space, without carinae laterally extending to clypeal apical margin, apex slightly to greatly above upper torular tangent, apex orthogonally angled forward and projecting anteriorly as a shelf of variable expanse, apical margin of shelf gently convex; disc of clypeus flat; epistomal sulcus laterally forming obtuse angle, medially sulcus obscured from view by clypeal protrusion; upper torular tangent at about head midlength; intertorular distance about 2× torular diameter; scape shorter than torulocellar distance; first flagellomere about as long as wide, slightly 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 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 2.5× as long as maximum width, maximum width slightly basad 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 with 1cu-a; three submarginal cells present (1rs-m present), second submarginal cell trapezoidal, anterior border (3Rs) significantly shorter than r-rs, r-rs at widest point of pterostigma; third submarginal cell about as broad as first submarginal cell; 1rs-m faintly arched, 2rs-m strongly arched, thus anterior border of third submarginal cell significantly shorter than posterior border of same cell, anterior border of third submarginal cell (4Rs) slightly shorter than combined lengths of r-rs and 3Rs; 1m-cu angulate in apical third near second submarginal cell, entering second submarginal cell distad cell midlength; anterior margin of hind wing with 5–6 distal hamuli arranged in an evenly spaced series; wing membranes hyaline clear; veins dark brown. Metatibia slender, elongate, length about 3.5× 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 longer than metatibial width, anterior margin with sparsely scatered simple setae and bristles, corbicular surface with sparsely scatered, erect, fine, simple setae; inner surface with keirotrichiate zone field covering most of surface except exceedingly narrow, posterior, slightly depressed (i.e., a weak clivulus present) glabrate zone and a rectangular apical glabrate zone, length of apical glabrate zone slightly less 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 roughly quadrate, longer than wide (only observed for H. proboscidea as metabasitari damaged in H. uraeus ), margins roughly parallel, apical margin comparatively straight, 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; metasomal sterna unmodified, with scatered, short, erect, fine, simple setae on sterna II– V; sting present.

ETYMOLOGY: The new genus-group name is a combination of the Ancient Greek Hā́idēs [ᾍδης, genitive singular, Hā́idou (ᾍδου)], the god of the underworld and realm of the shades, and Melikertes , type genus of the tribe. The name is an allusion to the haidomyrmecine ants who are famed for their peculiar and often extreme facial and mandibular modifications (e.g., McKellar et al., 2013; Perrichot et al., 2016, 2020; Barden et al., 2020). The gender of the name is masculine.

Key to Species of Haidomelikertes

1. Clypeal protrusion extending well above upper torular tangent, apex angled anteriorly and extending forward as prominent shelf ( Figs. 23, 25 ), with dorsal-facing surface about 2× torular diameter, neck of clypeal protrusion between antennal toruli slightly narrower than apex ( Fig. 23 ); slightly larger species, length ca. 4.1 mm ..................................................................... H. proboscidea (Engel)

—. Clypeal protrusion only slightly extending above upper torular tangent, apex angled anteriorly and extending forward as thin, lamellate shelf ( Figs. 24, 26– 28 ), dorsal-facing surface about a torular diameter or slightly less in length; neck of clypeal protrusion not narrowed relative to apex ( Fig. 24 ); slightly smaller species, length ca. 3.3 mm ........................................ H. uraeus Engel, n. sp.

Figures

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 27–28. Oblique facial views of holotype worker of Haidomelikertes uraeus, new genus and species (SMF Be 14263a). 27. Slightly dorsal left oblique; white arrow points to apex of facial protuberance. 28. Slightly ventral right oblique.

Figures 19–20. Inner (retrolateral) surfaces of metatibiae of Haidomelikertes, new genus, and Aethemelikertes, new genus. 19. Haidomelikertes uraeus, new species, holotype worker (SMF Be 14263a). 20. Aethemelikertes emunctorii, new species, holotype worker (SMF Be 14262a).