Palaeomacropis eocenicus, Michez & Nel & Menier & Rasmont, 2007

Michez, Denis, Nel, Andre, Menier, Jean-Jacques & Rasmont, Pierre, 2007, The oldest fossil of a melittid bee (Hymenoptera: Apiformes) from the early Eocene of Oise (France), Zoological Journal of the Linnean Society 150 (4), pp. 701-709 : 705-706

POSITION OF PALAEOMACROPIS EOCENICUS GEN.

NOV. SP. NOV. IN APOIDEA

Palaeomacropis eocenicus is an ST bee because of its similar cylindrical labial palpal segments ( Michener, 2000). Thus, P. eocenicus is not a Megachilidae or an Apidae . The attribution to a precise taxon within ST bees is complicated by the poor preservation of the glossa.

Palaeomacropis eocenicus cannot be included in the Australian family Stenotritidae because of its antennal structure. The first flagellar segment of Stenotritidae is longer than the scape, unlike the case of P. eocenicus .

Palaeomacropis eocenicus does not have glossa with bifid apex. This would exclude it from Colletidae . However, Xeromelissinae ( Colletidae ) has the same kind of metasomal setae as P. eocenicus . It has long, erect to suberect setae on S1, S2, S3, S4, and S5, distinctly longer on S2 than on the other sterna ( Michener, 2000). Xeromelissinae is strictly Neotropical, with two fossils currently included in this group, Chilicola (Hylaeosoma) electrodominicana Engel, 2000 and Chilicola gracilis Michener & Poinar, 1996 , both found in Dominican amber ( Michener & Poinar, 1996; Engel, 2000). Palaeomacropis eocenicus differs from the Xeromelissinae as follows: the episternal groove is ventrally inconspiscuous; the stipes, prementum and cardo are not very long; the second submarginal cell is not much shorter than the first; the setae on S2 and the other sterna are apparently not branched or plumose; the stigma is basal to vein r with margins apically diverging (this latter character is present in Chilicolini and Geodiscelis Michener & Rozen, 1999 ) ( Michener & Rozen, 1999; Engel, 2000). Therefore, Palaeomacropis eocenicus cannot be considered as a Xeromelissinae.

Specialized metasomal setae are also present on the metasoma in the halictid genus Homalictus Cockerell 1919 ( Alexander & Michener, 1995). Homalictus differs from P. eocenicus in the enormous scopal hairs that it has on the sterna and the ventral part of the terga, and the plumose scopal hairs on its hind femora and tibia ( Michener, 2000).

Among other groups, P. eocenicus differs from Andreninae due to its lack of paired subantennal sutures or facial foveae. It differs from the Oxaeinae ( Andrenidae ) and Diphaglossinae ( Colletidae ) in the presence of a stigma longer than the prestigma, with vein r arising well before the apical margin of the stigma, and the convex margin of the stigma in the marginal cell. Palaeomacropis eocenicus differs from the Colletinae ( Colletidae ), Halictinae ( Halictidae ), and Nomioidinae ( Halictidae ) in its weak episternal groove, mainly dorsal and almost disappearing ventrally (this structure is also absent in the colletine Hesperocolletes Michener, 1965 ). The Nomiinae ( Halictidae ) also have a reduced episternal groove, as is the case in P. eocenicus . Nevertheless, their marginal cell usually does not taper much toward the apex, unlike P. eocenicus ( Michener, 2000) , although some nomiine species do have pointed marginal cells. The Nomiinae typically have a labrum with a strong apical process in the female, unlike P. eocenicus .

Unlike P. eocenicus , the Baltic amber family Palaeomelittidae Engel, 2001 has no long, erect setae on the metasomal sterna. However it does have a well developed jugal lobe ( Engel, 2001), which P. eocenicus does not.

Palaeomacropis eocenicus and Melittidae are ST bees and they have in common the absence (or near absence) of episternal and scrobal grooves. Their jugal lobe (on the hindwing) is clearly shorter than the vannal lobe (characters shared with LT bees). The middle coxa of Palaeomacropis eocenicus is fully exposed laterally and nearly reaches the lower metapleural pit, as in contemporary species Melitta (character shared with LT bees) ( Michener, 2000).

In conclusion, P. eocenicus is an ST bee, with a fully exposed middle coxa, without facial foveae or paired subantennal sutures, and with the jugal lobe shorter than the vannal lobe. Therefore, we include P. eocenicus in Melittidae .