More from the Eocene Belgian amber: a new ladybird fossil of the genus Rhyzobius Kugelann (Coleoptera: Coccinellidae)

Abstract

Very few insects are known from the Eocene Belgian amber. Only one termite and one true bug have hitherto been described. Here we describe the ladybird Rhyzobius belgicus sp. nov., from this amber. Together with Rhyzobius antiquus, and R. gratiosus from the nearly contemporaneous Oise amber (France), it provides a novel insight on the early diversity of Coccinellidae during the Lowermost Eocene. Nephus subcircularis, also from the Oise amber, is excluded from this genus and considered as a Coccinellidae incertae sedis after reexamination of the holotype. Also Scymnus angulatus and ‘Scymnus (Pullus) aff. kawamurai’ are Coleoptera incertae sedis. Thus there is no longer accurate fossil Scymnini. Curiously, the Coccinellidae are quite infrequent in the Oise amber. The discovery of this new fossil and its assignment to the genus level is significant, as fossils are often used as calibration points in ladybird molecular phylogenies, thereby enabling analyses of the temporal evolution of lineages. The biology of the extant Rhyzobius species remains inadequately documented. Nonetheless, it has been suggested that they can potentially exploit coccid and aphid colonies at earlier and/or later developmental stages. Although coccids and aphids (coccinellid prey) are unknown in the Belgian amber, they are well present in the Oise amber.