Diagnosis of the Merodon desuturinus lineage

The specific shape of the lateral sclerite of the aedeagus (gradually tapered, with the tip curved downwards) is the main synapomorphic character that connects all species of the group (Fig. 1C: s). Species in this group have pile on the posterior side of mesocoxa, a curved distal prolongation of anterior surstylar lobe (Fig. 1B: al), basoflagellomere less than two times as long as wide (Fig. 2A), scutum without pollen (Fig. 2B) or with less distinct pollinose longitudinal vittae, wing microtrichose between veins R1 and RS (Fig. 2C: marked with arrow) contrary to bare area in species from the morphologically related M. albifrons lineage, postpronotum usually brown or yellow-reddish, and pilosity on lateral side of tergum 4 in female long, medially short and mostly adpressed (Fig. 2D).