A new genus was proposed for three species formerly assigned to the genus Phyllonorycter Hübner, including an invasive species to Belgium feeding on Robinia pseudoacacia L. The decision on the erection of a new genus is based on the evidences of the detailed morphology of adults, pupae, larvae, and life histories, and of DNA characters. Distribution patterns of the invasive species and its relatives are presented. I demonstrate the case for which there is a mismatch between the DNA barcode (COI gene) and 21 protein coding nuclear genes. Only a multi gene analysis revealed divergent clusters of the known Gracillariidae genera and a careful re-inspection revealed morphologic diagnostic characters associated with several of those genetic clusters. I shortly present the new classification of the order Lepidoptera based on morphology and molecular characters. I discuss the significance of taxonomic history demonstrating the consequences of some publications as old as 150 years to present-day, modern science.