Mesopolobus incultus auct. (Hymenoptera: Pteromalidae) contains two distinct species: Mesopolobus incultus (Walker, 1834) and Mesopolobus amyntor (Walker, 1845)
Mesopolobus incultus auct. is hypothesized to consist of twodifferent species, M. amyntor (Walker) and M. incultus (Walker). This hypothesis is supported bymolecular(cytochromec oxidase subunit I, i.e. COI), morphological and biologicaldata.Mesopolobus amyntor is a primary parasitoid of Mecinus pascuorum (Gyllenhal) and M. labilis (Herbst) (Coleoptera: Curculionidae) on Plantago lanceolata. Mesopolobus incultus is a primary parasitoid of Protapion fulvipes (Geoffroy) (Coleoptera: Apionidae) on Trifolium repens and T. pratense, and hasalso been inferred to act as a secondary parasitoid (hyperparasitoid) of Spintherus dubius (Nees) (Hymenoptera: Pteromalidae) or Bruchophagus gibbus (Boheman) (Hymenoptera: Eurytomidae). The results of this study lead to following nomenclatural changes: M. amyntor is removed from synonymy under M. incultus, and Pteromalus urgo, P. belesis and P. berecynthos, all described by Walker, are synonymized under M. amyntor. The species are diagnosed with characters illustrated.