Hide-and-seek with hoverflies: Merodon aureus – a species, a complex or a subgroup?

In order to disentangle the currently confused interpretations and nomenclature ofMerodon aureusandM. aeneus, we have reviewed all existing type material and species names known to us as assigned synonyms of these taxa. We resolveM. aeneusas being a junior synonym ofM. aureus. We designate a lectotype forM. aureusand a neotype forM. aeneus.Additionally, we provide evidence thatM. aureus, together with two newly discovered taxa (M. calidussp. nov.andM. ortussp. nov.), represent a complex of cryptic species named theM. aureusspecies complex. This complex, together with theM. unicolorspecies complex and the speciesM. pumilus, is part of theM. aureussubgroup. TheM. unicolorspecies complex comprises two cryptic species:M. unicolorandM. albidussp. nov. The new species are described by applying an integrative taxonomic approach using several data types (COIand 28S rRNA genes, geometric morphometry of the wings, ecological and distributional data). Based on theCOIgene sequence analysis and distributional data, the pupa previously described as an immature stage of the speciesM. aureusis redefined as an immature stage of the new speciesM. calidus. Speciation within theM. aureussubgroup is discussed in the context of the phylogeographic history in the studied region.