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.