Large numbers of five invasive land snail species were observed crawling around at the Dellewal in West-Terschelling. Terschelling is an island in the Wadden Sea and is part of the province of Friesland. The snails belonged to the Helicid species Arianta arbustorum and Cepaea nemoralis, and the Hygromiid species Candidula intersecta, Cernuella virgata and Monacha cantiana.