Four peculiar new <em>Metallactus</em> species from Argentina (Coleoptera: Chrysomelidae, Cryptocephalinae)
Keywords:Entomology, taxonomy, new species, Pachybrachina, Neotropical Region, endophallus, endophallic sclerites
Metallactus canescens sp. nov., Metallactus aemulus sp. nov., Metallactus diaguita sp. nov., Metallactus nugator sp. nov. are described from Northern and Central Argentina. The new species are very similar to one another regarding their external look but can be distinguished above all on the basis of internal characters, in particular the morphology of the aedeagal median lobe. Besides, some traits of their external features, i. e. the thick dorsal setosity and the weak metallic hue, look quite uncommon within the genus Metallactus Suffrian, 1866 and remind of some species of genus Coscinoptera Lacordaire, 1848 (in particular C. tibialis Harold, 1875) and other undescribed species belonging to the genus Griburius Haldeman, 1849. This might be due to some kind of adaptive convergent evolution.