29-Apr London’s April Snails: Spiral Secrets

Most snails spiral dextrally i.e. to the right which means if you hold the snail up vertically its mouth will be set slightly to the right but we do have some in London that spiral sinistrally i.e. to the left, in which case their mouth is set slightly to the left.

There are a small number of large species which are found in our gardens and along the North Downs, otherwise the rest inhabit a wide range of different habitats including trees in woods, life litter, fallen logs, hedges, under stones, waste areas but not heathland. The best time to look for them is on warm wet days either after or during rain or at night with a torch. The most familiar of all is the Garden snail, already mentioned, which is also one of the most variable.

It usually has five whorls, a blunt spire, five cross bands with some streaking and flecking. However, it can vary from almost black to almost white, be glossy or dull and have a thick or thin shell. The problem for gardeners is that they lay one hundred eggs at a time, live for up to five years and if one is thrown into the next door garden it will probably return in less than a day. They also have “roosts” which are safe places such as walls or terracotta pots which they constantly return to, to avoid detection. In the past Londoners even ate them, calling them wall fish.

The largest in our area is the Roman snail H. pomatia (50 mm) supposedly introduced by the Romans because of its edibility. Certainly this is still the one we see served up in restaurants complete with its creamy coloured coarsely striated shell. Now thankfully protected in the wild they can still be found beside hedgerows and on chalky banks along the North Downs. In another month or so they are sometimes found half buried in which case they will be laying their eggs. Two other of our larger, more familiar land snails are the White-lipped snail Cepaea hortensis and the Brown-lipped snail C. nemoralis. Both are about 2 cms wide with the White-lipped usually being slightly smaller. They are famous for the variety of their colours and banding of which there are more than eighty different types.

The White-lipped snail is normally yellow but the Brown-lipped snail can be white, brown, yellow or even pink. Both can have either no stripes or either one, two, three, four or five although brown snails with five stripes are the norm. Such polymorphism has been of great interest to evolutionists who have had great difficulty in explaining what evolutionary advantage such a wide variation can give. They happen to be a favourite food of song thrushes and their broken shells are often found around their “anvils”.

Perhaps the birds see certain patterns better than others in different habitats. The best way to tell the two snails apart is just to look at their lips i.e. the edges of their apertures, but here again there is more variation with the White-lipped snail sometimes having brown lips and Brown-lipped snail red ones.

Another smaller garden snail well-known as a pest in strawberry beds is the Strawberry snail Trichia striolata) (13 mm wide). It is the classic ramshorn shape but with many fine striations and a slightly lighter-coloured coil as it nears the aperture. The Garlic glass snail Oxychilus alliarius (14 mm) is also found in gardens. It is shinier than the Strawberry snail with a transparent orange glass-like shell from which a blue-black snail emerges smelling distinctly of garlic.

Quite a number of our smaller snails are found in woodland. Three with similar attractive cudgel shapes which spiral sinistrally are the Plaited Door snail Cochlodina laminata (16 mm), the Two-toothed Door snail Clausilia bidentata (13 mm) and the Tree Snail Balea perversa (8 mm). The Plaited Door snail has up to twelve coils, one tooth projecting in its aperture and is either reddish-brown or yellow-brown. The Two-toothed Door snail has twelve to fourteen coils, two teeth and is more horn-coloured with white striations and the Tree snail, which is much rarer, has only six to eight coils, no tooth and is yellowish-brown. The first two spend the day among tree roots looking not unlike fallen beech buds, whereas the latter snail is much more truly arboreal, rarely being found on the ground. As they feed on lichens they all tend to be absent from polluted areas. Their teeth are said to deter predators from entering their shells.

Other snails are often covered in tiny hairs or prickles, the function of which is still not fully understood. The Hairy snail Trochulus hispidus (6 mm) is one such common species. It has rows of transverse hairs which often wear off. The Prickly snail Acanthinura aculeate (2 mm) is another with tiny flexible spines. The first is often found among fallen leaves or on rotting logs and the second is said to climb trees and then return to the ground on leaves as they fall. Another woodland species well-known for slipping through your fingers is the glossy-brown Slippery Moss snail Cochlicopa lubrica (6 mm).

Not surprisingly as snails need calcium carbonate to build their shells they are more common in chalky areas and rarely found in acidic heathland. Other than the impressive Roman snail, the Land winkle Pomatia elegans (10 mm) the Pellucid Glass snail Vitrina pellucida (5 mm) and Lovely Vallonia Vallonia pulchella (2 mm) are all worth looking for. The Land winkle looks for all the world like a small edible winkle with its perfectly circular aperture. The Pellucid Glass snail has a shell not unlike green glass and is sometimes still active in the winter. It feeds on earthworms and is often found near horse droppings. The Lovely Vallonia has a name which gives testament to its looks. It has a delicate ivory-white crystal-like shell with a flared aperture and milky-white body. Just occasionally it is found in numbers after rainstorms.

Marshes and wet meadows are also good for snails. Two handsome species to look out for are the Amber snail Succinea putris (10 mm) and the Crystal snail Vitrea crystallina (2.5 mm). The Amber snail has a thin glass-like amber-coloured shell and the Crystal snail a shell that has been likened to rock crystal. Sometimes the ends of the tentacles in Amber snails look noticeably more swollen. This is likely to be due to a parasitic infection which them gets passed on to birds as they tend to notice them more. Once eaten the parasites develop into flukes within the birds.

Other habitats favoured by snails are odder than you might think. The Rounded Snail Discus rotundatus (6.5 mm) is fond of churchyards. It is particularly handsome with many tight coils, transverse striations and red flecks. Another is the Blind snail Ceciliodes acicula (4 mm) which prefers to remain underground among the tombs, hence its other name the Grave-diggers snail. The Kentish snail Monacha cantiana (14 mm high and 20 mm wide) likes hedges where there are lots of nettles and also railway embankments. It has a creamy mottled shell with tinges of red. It is a common, introduced species that has long since fled Kent where it was first identified. Draparnaud’s glass snail Oxychilus draparnaudi (12 mm) likes waste areas and even roadside rubbish.

It is horn coloured and waxy in appearance although the snail itself is an alarming deep blue. Although ubiquitous the Dwarf snail Punctum pygmaeum is rarely found due to its tiny size. Although the classic turret shape it is usually less than a millimetre in height, occasionally soaring to 1.5 mm. One last curiosity is the very attractive spindle-shaped Italian door snail Papillifera papillaris (10 mm). It is believed to have arrived in Britain on a marble balustrade imported from the Villa Borghese in Rome to Clivedon House in Berkshire which it may still possibly be adorning.

Other than Bookham Common, which boasts over fifteen different land snails, Lesnes Abbey wood is worth visiting for a chance of seeing the lens-shaped Lapidary snail Heliciogona lapicida (7 mm high, 17 mm wide) although it does like to climb high in trees. One of the best bits of the North Downs to look for snails is the remote Quarry hangers area (sssi) near Merstham.