Taxonomic decision as a compromise: Acasis appensata (Eversmann, 1832) in Central Italy—a case of conflicting evidence between DNA barcode and morphology (Lepidoptera: Geometridae)

Acasis appensata (Eversmann, 1842) (Lepidoptera: Geometridae), distributed from central and northern Europe to eastern Asia, was collected in the Mediterranean (Central Italy, Abruzzi) for the first time. Adults from this region differ significantly from nominotypical populations in external appearance and in the 5’ barcode fragment of the CO1 gene (barcode). However, morphology of male and female genitalia falls completely within the range of variation of A. appensata, resulting in conflicting evidence with respect to its taxonomic status. Considering the striking differences in genitalia morphology between the two European species of Acasis, viz. A. appensata and A. viretata (Hübner, 1799), the population from the Abruzzi is not validated as different at species level but described as the subspecies A. appensata callaina ssp. nov. The habitus and male and female genitalia of European taxa are figured.