Migration pattern of the red admiral, Vanessa atalanta L. (Lepidoptera, Nymphalidae), in Italy

Systematic observations on seasonal incidence of the red admiral (Vanessa atalanta L.) in central-northern Italy were made in the course of four successive years. Our data show that our region is characterized by regular bidirectional migration which is particularly remarkable in October, during autumn migration to the overwintering sites. Red admirals' migration is highly directional: individuals fly along straight lines at the mean speed of 14 km/h, and produce highly oriented distributions of their vanishing bearings. This directional preference is not the result of passive displacement caused by winds, but is the expression of an internal tendency based on the use of a compass mechanism. Red admirals' seasonal incidence in our area significantly differs from that reported for the northern range of this butterfly species. This study constitutes the base of a long-term investigation aimed at clarifying the phenology and other aspects of migration of this butterfly species (origin and destination of migrants, mechanism of orientation) which, despite the amount of literature on this subject, are as yet not entirely understood.