Verticale verspreiding en biogeografie van dagvlinders in de westelijke Alpen (Lepidoptera: Rhopalocera)

The altitudinal succession of butterflies is studied and discussed for Vanoise (French Alps) in comparison with the Valle d'Aosta (Italian Alps), both areas being contiguous. The chorological- index method, introduced by Kudma ( 1986), is used in relation with altitudinal faWla differences. The decrease offaunal affinity is studied, according as the difference in altitude increases. The relative value of the fauna, however, increases with the increase of altitude. Finally the biogeographical composition of the butterfly fauna in the area is studied. At least 60% of all species with a high chorological index value belongs to the European and Sub-mediterranean fauna element.