& Cepaea nemoralis (Grove Snail)
British distribution: Both species widespread and generally common, C. nemoralis rare or absent in northern Scotland, C. hortensis extending north to Shetland.
Both species widespread in N.W. Europe, C. hortensis extending into the Arctic, occurrence of both species elsewhere to be checked.
Shell colour extremely variable, ranging from uniform yellow to yellow with dark brown spiral bands; lip of shell almost always white. Locally common throughout Britain and Ireland. Favours wide range of habitats including woods and hedges.
Banded morphs (especially banded yellow) are known to predominate in grassy habitats, where the bands are presumed to provide camouflage amongst the linear, often vertical shadows, whereas unbanded morphs (especially unbanded pink and unbanded brown) show preference for wooded sites. However, polymorphism is retained in these populations since they often occupy marginal or boundary habitats (notably wood and scrub margins, and roadsides with long grass backed by hedgerows). Heterozygote advantage is also involved.
Both species occur in very varied habitats, including woodland, hedges, fens, open grassland and dunes. C. nemoralis is evidently the commoner of the two in warmer, dryer habitats in the south.
They are highly polymorphic in shell colour and banding, and light and dark body colour morphs also occur. C. nemoralis has been (supposedly) much the more studied and it occurs in three main colours: brown, pink and yellow, with brown dominant over the other colours, and pink dominant to yellow. More than one allele is known for each of these colours and there is also a 'tawny' morph that occurs in sand dune populations. Bands may be present or absent (unbanded dominant to banded) and there is further variation in number and pigmentation of bands.