Insights from the preimaginal morphology of the constans species-group, to reveal novel morphological patterns of the Merodon albifrons-evolutionary lineage (Diptera, Syrphidae)

Merodon triangulum Vujić, Radenković & Hurkmans, 2020 is a european endemic hoverfly species belonging to Merodon constans species group, inside albifrons lineage. The distribution of this species is known to be mostly central Europe and Balkan peninsula and it has been categorized as Near Threatened in the European IUCN red list of hoverflies (Janković and Radenković 2021); this paper cites the species for the first time in Ukraine (western Ukraine, specifically). In the present study, the preimaginal stages of this species are described and figured using Scanning Electron Microscopy. The material used for the descriptions were larvae collected in Ukraine and Serbia feeding inside underground storage organs of the plant Leucojum vernum L., 1753. This morphological description constitutes the first one inside the constans species group, and the sixth description of the albifrons lineage, in which there is only one species group left to have at least one species of the preimaginal stages described ( ruficornis group). The descriptions were compared with the rest available of the genus, stating the diagnostical characters of the present species and the shared characters inside the lineage. The relationship between preimaginal stages and Leucojum bulbs is stated for the first time for constans species group.