We used the COI marker, the most popular DNA barcode for the animal kingdom, to assess the taxonomic status of Corsican populations of eight groups of species of ants that occur both on Corsica and the European mainland. (i) In two groups, we detected no genetic differentiation between Corsica and the continent. Absence of differentiation across varieties of Aphaenogaster spinosa within Corsica confirm current synonymies. (ii) In four groups, we detected strong genetic differentiation between Corsica and the continent, confirming recent taxonomic studies based on morphology for three of these groups. For the fourth group, we propose that the status of Corsican populations be raised from sub-species to species: Temnothorax cordieri stat. rev. (iii) In one group, the genetic differentiation and morphological differences do not support splitting and as a consequence we propose to accept the previous synonymy Temnothorax tuberum = Temnothorax melanocephalus. (iv) In Myrmica scabrinodis and Myrmica spinosior, COI sequence information is largely inconsistent with morphology and geography, not only on Corsica but also on the mainland, and should not be used to support taxonomic decisions. Although the use of COI has drawbacks, it is globally consistent with morphology and can be used to complement morphological ant taxonomy. We provide an updated checklist of ants of Corsica.