Revision of the mainland African species of the Old World social wasp genus Ropalidia Guérin-Méneville 1831 (Hymenoptera; Vespidae)

A revision of the African species of the social wasp genus Ropalidia Gurin-Mneville is given (excluding Madagascar). It is based on 5,717 examined specimens and 528 documented field observations. A taxonomic revision, mitochondrial COI and 28S rDNA are provided, alongside a hypothesis-free morphometric analysis of female head shape based on 42 pre-defined landmarks assignments. In addition to 15 valid or re-established species, 33 new species are described here (R. acuminata sp. nov., R. amanhii sp. nov., R. aulaeum sp. nov., R. baki sp. nov., R. barbata sp. nov., R. caesariata sp. nov., R. clepsydra sp. nov., R. copelandi sp. nov., R. dondo sp. nov., R. flavoscutelata sp. nov., R. fita sp. nov., R. haladaorum sp. nov., R. hastata sp. nov., R. kitui sp. nov., R. kuficha sp. nov., R. luculenta sp. nov., R. mabawa sp. nov., R. macloutsie sp. nov., R. makore sp. nov., R. mangoflava sp. nov., R. mosichi sp. nov., R. nigrocerasina sp. nov., R. nubila sp. nov., R. ophuzi sp. nov., R. perovici sp. nov., R. retromaculata sp. nov., R. salebrosa sp. nov., R. sandamara sp. nov., R. soikae sp. nov., R. tajiri sp. nov., R. tenebrica sp. nov., R. tenuipilosa sp. nov., R. valentula sp. nov.). Males of eight known species are described for the first time. Genetic sequences were very useful for species separation, although there were some exceptions; the most notable exception was R. guttatipennis (de Saussure), with 25 COI genetic lineages recorded in a single morphospecies. The African species of the genus Ropalidia are characterized by the substantial overlap of intraspecific and interspecific variation, diverse genetic lineages and numerous local and endemic speciation processes.