A successful habitat patch creation for Zerynthia cassandra

Zerynthia cassandra (Geyer) (Lepidoptera Papilionidae) is a butterfly species endemic to Italy, which was recently split from the Habitats Directive species, Zerynthia polyxena (Denis et Schiffermuller). The distribution of Z. cassandra is fragmented, limited to microhabitats where the larval food plants (Aristolochia spp.) can grow. The creation of new habitat patches can increase habitat availability and connectivity, thus improving the chances of survival of this species. This study relates on the creation of a new habitat patch in a 320,000 m2 park in the province of Bologna (Northern Italy), 8-15 Km distant from natural patches occupied by Z. cassandra. Fifty rootstocks of the local larval food plant, Aristolochia rotunda L., were introduced in 1982 in a 5 × 30 m belt along the edge of a pond. From the 1990s onwards, the management of the park became more conservation-oriented and favoured the spread of A. rotunda, that is now abundant. In 2016, the new habitat patch was spontaneously colonized by Z. cassandra. The number of adults and the areas where eggs and larvae were found increased in 2017 and 2018, the presence of 67 adults was estimated in 2018, so Z. cassandra appears to be now well established in the park. In the light of this experience, criteria for the selection and management of sites for the creation of new habitat patches are suggested and discussed.