Populations of Cepaea Hortensis (O. F. Muller, 1774) polymorphic for the colour of shell lip in north-western Poland and north-central Germany

In Cepaea hortensis (O. F. Müller), the shell lip (peristome) is usually white. In most areas the lip colour allows us to reliably distinguish this species from C. nemoralis (Linnaeus) in which the lip is usually dark brown. Populations polymorphic for lip colour are rare and occur only locally. Here I report on populations of C. hortensis containing dark-lipped individuals in north-western Poland and in north-central Germany. The frequency of dark-lipped individuals ranged from 3% to 31%. It was common in brown and pink shells, but occurred only sporadically in yellow shells. No selective factors promoting dark-lipped C. hortensis are evident. The occurrence of this phenotype is likely to reflect random events.