The garden snail

The snail people mean, in a European or North American garden, is often Cornu aspersum, still called Helix aspersa in older books. The shell is a rounded cone, brown to olive, usually flecked and banded, with a large opening and, in adults, a pale reflected lip. A full-grown shell is often about 25 to 40 millimetres across. That is big enough to notice on a wet brick and small enough to miss under a leaf of chard.

The species is native to the Mediterranean and has traveled with people, plants, and soil into much of the temperate world. In many gardens it is an ordinary resident and an occasional pest of seedlings. In a few agricultural regions it is a more serious problem. The animal in a mild coastal allotment and the animal in an irrigated lettuce field are the same species, limited mostly by how long the air stays damp enough for feeding.

Cornu aspersum grazes living soft growth, algae, and decaying vegetation. It needs calcium for the shell and will rasp mortar, soil, and the shells of the dead. It mates using a love dart, buries its eggs, and seals itself away when the day is too dry or too cold. Individuals can live several years. Five years is a figure often repeated for protected animals, not a guarantee in a bed that also contains thrushes and spades.

If you learn one shell, learn this one well enough to stop calling everything else by its name. A yellow shell with crisp dark bands is probably a Cepaea. A tiny glossy amber snail in the litter is another family. A long shell in a pond is not this animal either. The habit of looking twice is the useful part of knowing a species. The name comes after the lip, the size, and the place.