
 
      Shell polymorphism in Cepaea
                  nemoralis
          
         
            Shell patterns in the common European land snail (Cepaea
                nemoralis) are determined genetically, and
            include variation in both ground color (yellow darkening to
            green) and presence or absence and extent of banding.
            Studies show that visual predators such as thrushes
            preferentially consume the less cryptic snails in any
            environment. Light, banded snails are more common in
            grasslands, whereas dark, unbanded snails are more common in
            dimly-lit woodlands.