Phylogenetic relationships of corbiculate bees have been a well-known
focus of controversies over the past 30 years. The majority of the morphological
datasets support the monophyly of Apina+Meliponina, whereas molecular datasets
recover Meliponina as sister to Bombina. This issue is especially critical to the
proper understanding of the evolution of clusters of traits that define the corbiculate
eusocial behaviour. This work provides a description and discussion on characters
of the head capsule, mandibles and sitophore of bees. Thirty-three characters
are proposed and optimized within concurrent phylogenetic hypotheses for corbiculate
bees, which results in seven derived character-states supporting the monophyly
of the Apina+Meliponina+Bombina and nine supporting the Apina+Meliponina
clades. Although some striking synapomorphies (e.g. tentorial bridge, pleurostomal
condyle, hypopharyngeal lobe) support the former clade, most characters supporting
the latter (i.e. Apina+Meliponina) were losses/reductions. Moreover, two previously
undescribed character transformations on hypostoma and sitophore favour the
Bombina+Meliponina clade. Internal head capsule characters are useful for phylogenetic
analysis in comparative studies of bees, and corbiculate bees in particular, when
efforts are made to solve the ‘corbiculate controversy’. An attempt ismade to standardize
the current terminology used for bees and for other Hymenoptera.