The once common Mazarine Blue (Cyaniris semiargus) has been extinct in the Netherlands since 1974. In 1996 a number of Mazarine Blues were sighted in Maastricht (province Limburg), in the most southerly tip of the country. The butterflies had spread from a colony in neighbouring Belgium, just a few kilometres away. The new site was in the city centre, in a nature reserve with an abundance of wild plants and flowers. In the following year specimens of the Mazarine Blue were recorded again. With skilful management of the site, this could lead to recolonization and the return of the species to the Netherlands.