SNAILS I N ARCHAEOLOGICAL EXCAVATIONS T H E E A R L OF C R A N B R O O K
Helix aspersa, the Common Snail, is the second largest snail found in the British Isles being only exceeded in size by H. pomatia, the Roman or edible snail. The two are much alike in shape but pomatia is considerably the larger, about 45 mm. in height and width as opposed to 35 mm. in aspersa. Both are edible and commonly eaten as food, and both are equally tasty when cooked in the conventional butter and garlic. It seems probable that both were introduced into this country if not by the Romans at least in the Iron Age, the often quoted Pleistocene records not having been substantiated. Like other edible creatures, the Great Afncan Snail being another example, H. aspersa has been introduced into many countries and flourishes in Orkney, New Zealand, the West Indies, St. Helena, Pitcairn Island, etc., etc. It is a gregarious creature roosting in colonies during the day in appropriate refuges, under stones, behind Vegetation growing against the wall of a house or at the base of trees, hedgerows, and the like. In limestone districts they are found roosting in vertical holes which seem to have been occupied and enlarged by successive generations of snails the mucus secreted by the foot being slightly acid. From these roosts they go out at night to feed, returning to the same place of refuge for the following day. If such a group is found and each individual marked with paint or nail varnish they will be found to be absent soon after dark and to have returned by the following morning, the remains of an absentee being sometimes recognised by paint on fragments of shell near a thrushes anvil. Fairly early in the winter, usually in October, they go into hibernation in similar colonies in similar retreats, sometimes burying themselves in the ground. They then close the mouth of the shell with a diaphragm made of dried mucus, called an epiphragm, which protects the animal from the cold and from desiccation by evaporation while it is torpid. As the cold weather increases it retreats further into its shell, a second and sometimes a third epiphragm being secreted as further protection. T h e epiphragm will also prevent the mouth of the shell being filled with mud if heavy rain carries silt into the hibernaculum. In the spring, usually sometime in April, they come out of hibernation. Mating then takes place after a fairly prolonged courtship, the animals caressing each other with their "horns" until both are sufficiently stimulated erotically to copulate. They then separate and each one, for they are hermaphrodite and each simultaneously acts as both male and female, digs a pit in the ground in which to lay its eggs. T h e snail then Covers the eggs with earth, and thus protected both from desiccation and predators, they are left to hatch on their own. Land snails are slow-moving