Thaumastobombus, ENGEL, 2001

ENGEL, MICHAEL S., 2001, A Monograph Of The Baltic Amber Bees And Evolution Of The Apoidea (Hymenoptera), Bulletin of the American Museum of Natural History 2001 (259), pp. 1-1 : 1-

Thaumastobombus , new genus

TYPE SPECIES: Thaumastobombus andreniformis Engel , new species.

DIAGNOSIS: This group superficially resembles in its general habitus a short­tongued bee (either an andrenine, rophitine, or melittine) as well as the dwarf honey bees [ Apini , Apis (Micrapis) ] (fig. 78; pl. 5f). It, however, readily falls away from the former by being a long­tongued bee and a corbiculate apine at that. From the latter it differs in the tribal characters [ Apini lacks metatibial spurs and outer mandibular grooves, has elongate eye hairs, an elongate malar space, among other features: refer to Engel (1999c) for a diagnosis of the honey bees and their constituent groups; however, note that in the subgeneric diagnoses for Apis presented in En­ gel (1999c), references to the shape of the first submarginal cell should refer to the third submarginal cell]. Among electrapines, Thaumastobombus is most similar to Protobombus , both sharing the quadrangular metabasitarsus. The former differs, however, by the linear epistomal sulcus and weakly emarginate compound eyes that converge below.

DESCRIPTION: Mandible with a few, weak apical teeth along upper half. Malar space short, shorter than basal mandibular width. Clypeus flat, not protuberant in lateral view. Epistomal sulcus linear (fig. 80). Inner margins of compound eyes slightly converging below, weakly emarginate (figs. 79, 80). F1 longer than F2, not longer than F2–3 combined; F3 longer than F2. Mesoscutal anterior border broadly rounded; median and parapsidal lines moderately impressed; scutellum projecting over metanotum and basal area of propodeum. Basal area of propodeum strongly declivitous (fig. 78). Keirotrichiate field not elevated; metatibial spur pectinate (figs. 83, 84); auricular basket dense, setae long (fig. 81); rastellum strong and formed of stiff setae (fig. 83); metabasitarsus about as long as wide (fig. 81). Margin of pterostigma within marginal cell convex; marginal cell apex offset from wing margin by slightly less than pterostigma width, apex appendiculate (fig 85). Worker gonostyli minutely setose at apices (fig. 78); sting not barbed (except see Thaumastobombus cf. andreniformis ).

ETYMOLOGY: The new genus­group name is a combination of the Greek words thaumastos (meaning ‘‘wonderful’’) and bombos (meaning ‘‘buzzing’’; a derivative of bombylios meaning ‘‘bumble bee’’). The name is masculine.

Thaumastobombus andreniformis , new species

Figures 78–85

Plate 5f

DIAGNOSIS: As for the genus (see above).

DESCRIPTION: Female. Total body length 6.92 mm; forewing length 4.45 mm. Head slightly wider than long (length 1.62 mm, width 1.70 mm). Upper interorbital distance 1.10 mm; lower interorbital distance 0.80 mm. Interocellar distance 0.45 mm; ocello­ cular distance 0.25 mm; median to lateral ocellus 0.14 mm. Distal third of clypeus set below lower tangent of compound eyes. Intertegular distance 1.20 mm. Basal vein basad cu­a by vein width; 1rs­m distad 1m­cu by seven times vein width; 2rs­m distad 2mcu by 2.5 times vein width; marginal cell apex separated from wing margin by onehalf pterostigma width, feebly appendiculate; first submarginal cell shorter than second and third combined; second submarginal cell narrowed, anterior border just less than onethird length of posterior border, anterior bor­ der just less than one­half length of anterior border of third submarginal cell; anterior border of third submarginal cell just less than one­third length of posterior border; seven distal hamuli, arranged in a single, evenly spaced series.

Integument of head and mesosoma smooth and impunctate. Terga and sterna imbricate.

Coloration not well preserved, apparently black and shining except antennae, metasoma, and legs dark brown; without maculations. Wing membrane hyaline; veins strong and dark brown.

Pubescence generally pale. Labrum with sparse, simple, erect setae. Setae of face numerous, simple, appressed, and short, each with a few, minute branches, setae partially obscuring integument, such setae intermixed with sparse, erect, minutely branched setae; setae most dense on face below level of antennal sockets and lateral to clypeus; appressed setae disappearing by vertex and erect setae becoming gradually more numerous. Gena with appressed setae like those of face; postgena with sparse, erect, moderate­ Sterna with dense, apical bands of moderate to long, simple setae.

MATERIAL: One specimen. Holotype. Female, worker caste, B­JH 164 ( AMNH) labeled: ‘‘Baltic amber: Eocene, Kaliningrad, Yantarny’’ // ‘‘ Holotype, Thaumastobombus andreniformis Engel’’.

ETYMOLOGY: The specific epithet is a reference to the superficial habitus of the species that resembles a short­tongued bee. The species also resembles to some degree the dwarf honey bees ( A. florea and A. andreniformis ), which also resemble short­tongued bees.

length, simple setae. Pubescence of mesoscutum as described for vertex. Tegula with a few, minute, appressed, simple setae. Scutellar pubescence as on mesoscutum except setae along posterior border elongate and plumose. Pleura with dense, long, plumose setae, partially obscuring integument. Posterior surface of metafemur with keirotrichiate zone on apical two­thirds; inner surface of metatibia with keirotrichiate zone not elevat­ ed but with narrow glabrous posterior margin that is one­fifth width of keirotrichiate zone, keirotrichiate zone separated from rastellum and metatibial apex by glabrous zone that is as long as width of keirotrichiate zone. Terga with sparse setal bands along apical margin, setae short and with a few, minute branches.

Thaumastobombus cf. andreniformis

MATERIAL: Two specimens. Non­type. Two females, worker caste, Nr. 9 ( CSUL) labeled: ‘‘ Thaumastobombus cf. andreniformis , det. M. S. Engel’’.

COMMENTS: These two, well­preserved individuals differ slightly in the shape of the head and particularly in the structure of metatibial spur whereby the thickening of the spur toward its apex present in the holotype of T. andreniformis (fig. 84) is apparently absent in both of these individuals. This specimen also appears to have microscopic barbs on the sting (perhaps also present in true T. andreniformis ?). These differences are likely not great enough to deserve specific status separated from T. andreniformis ; however, I hesitate to place them immediately into T. andreniformis until more material of the genus is discovered. If these differences continue to be upheld or are found to be congruent with additional, yet undiscovered, characters, then specific status for this morph would be warranted.

MELIKERTINI , New Tribe

TYPE GENUS: Melikertes Engel, 1998 a.

DIAGNOSIS: This group most closely resembles species of the stingless bee tribe Me­

TABLE 9 Hierarchical Classification of Tribe † Melikertini

liponini. The general habitus of all species is Trigona ­like. The melikertines differ from the Meliponini by the complete wing venation, presence of a single metatibial spur, presence of a supraalar carina, toothed claws, presence of an auricle, and presence of a sting.

DESCRIPTION: Small to moderate size (ca. 3–8.5 mm long), slender, sparsely pubescent bees. Mandible without outer mandibular grooves. Labral width 3–4 times length. Clypeus gently convex and weakly protuberant in profile. Compound eyes bare. Supraälar carina present; scutellum broadly rounded posteriorly and variously produced (ranging from projecting over metanotum and propodeum to not projecting over metanotum). Claws of female with minute, inner tooth (figs. 89, 90, 108); arolium strong and present (e.g., fig. 108); single, reduced metatibial spur present (figs. 90, 102, 107); malus of strigilis with short anterior prong in addition to primary ventral velum; metabasitarsus with distinct auricle at base (figs. 89, 90, 106, 107); metatibia without penicillum. Distal venation of forewing strong and present (figs. 91, 103, 109); marginal cell large and narrowly rounded at apex, slightly offset from wing margin, feebly appendiculate, cell longer than distance from its apex to wing apex; pterostigma present and moderate size, much longer than prestigma, r­rs arising near or just beyond midpoint, margin within marginal cell convex; 1m­cu angled; hind wing with distinct jugal lobe, lobe broadly and deeply incised (figs. 92, 104, 110); hamuli reduced; wing membrane without alar papillae. Sting not reduced; apparently not barbed.

COMMENTS: This is a particularly diverse group of Baltic amber bees and specimens seem to be relatively commonly encountered. Table 9 summarizes the classification of the tribe as I have outlined it herein.

Figures

Fig. 78. Left dorsolateral habitus of holotype female of Thaumastobombus andreniformis, new species. Scale bar = 1 mm.

Fig. 79. Frontal view of head of holotype female of Thaumastobombus andreniformis, new species.

Fig. 80. Frontal view of head of holotype female of Thaumastobombus andreniformis, new species. Scale bar = 0.5 mm.