WAYS OF THE WILD.

Auckland Star, Volume LXVII, Issue 205, 29 August 1936, Page 1 (Supplement)

WAYS OF THE WILD.

SNAIL COLONISTS. horde of tjndesered IMMIGRANTS. (By A. W. B. POWELL.) It often happens that the common plants and animals of a particular country arc not necessarily natives of that land. Everyone knows the common garden snail,. but does everyone know that it is not a true New Zealander, but a self invited colonist from Europe?

Originally the garden snail,. Helix aspersa, was a native of Northern Europe and the British Isles, but with the advent of international trade the species has become almost cosmopolitan, having been transported accidentally along with merchandise and produce. _ These snails are very hardy and will endure extreme heat and cold alike. They are equally at home in the gardens of Europe and those of the Antipodes, and have been established by art or by accident in Nova Scotia, South Carolina, New Orleans, California, Mexico, Cuba, Hayti, Brazil, Valparaiso, Capetown, the Azores, St. Helena, Mauritius, Lovalty Islands, Australia and New Zealand. The first New_ Zealand record of this accidentally introduced species was from Nelson in IS6I, but it has since spread rapidly by means of shipping to most of our seaports, and is now steadily invading inland areas. I have found it lining among lupins on sandhills in North Auckland, and it has even invaded the lonely Cape Maria van Dieman Island, which is visited by the Government steamer only three or four times a year. Nightmares For Weeks. If our garden enthusiasts had just one peep through a microscope at the dental apparatus of the garden snail, in all probability they would be troubled with nightmares for weeks afterwards. Every species of snail has an efficient dentition which is adapted for the kind of food taken, just as in the higher mammals. Herbivorous snails have blunt chisel shaped teeth somewhat like those of a horse or cow, while the carnivorous snails have sharp fangs reminiscent of those of the tiger. The marvel of the garden snail's set of teeth, liowe\ or, lies in the fact that they number over 16,000. Is it any wonder that vegetables disappear in a night; and what must a snail feel like after a hout of toothache?

Equally common m New Zealand gardens are some twelve species of slugs, which with one exception are voracious vegetarian feeders, and like the garden snail are all accidental importations from Europe. The one introduced slug with a good reputation is the large tiger-slug, a greyish creature liberally spotted .and striped with dark brown and growing up to four inches in length. This slug is a carnivorous feeder living mostly upon the smaller vegetarian slugs and thus does excellent service in the garden. Unfortunately its large size and conspicuous appearance makes this slug an easy victim to the infuriated gardener seeking to preserve his plants from the ravages of snails and slugs generally. It is to be hoped that the virtues of the tiger-slug will become more generally known so that they may be spared to do the good work they are so fitted to do in keeping a check upon the vegetarian kinds.

Another introduced, snail widely distributed in New Zealand is Hyalinia cellaria, a smooth, glossy, flat snail, about half an inch in diameter. It is usually found under clumps of grass and even stones and pieces of wood in city and suburban gardens. No native species of snails, of which there are 203 species, will live in cultivated surroundings, so in time our unique native snail fauna will be replaced almost entirely by these hardy importations from Europe. Smaller Kinds Harmless. A tiny introduced English snail about an eighth of an inch across, Yallonia excentrica, was found quite abundantly in Albert Park, Auckland, in IS9O, but apparently has not been found since. Two other small English snails, Cionella lubrica and Caecilianella acicula, seem to be increasing locally. The former is now quite common in the Auckland Domain under decaying oak leaves, and the latter occurs in gardens around One Tree Hill, Auckland. These smaller kinds feed on decaying vegetation and are quite harmless to living plants. Many methods of control have been tried for snails and slugs, but most of them entail considerable time and expense, with little effect. The sprinkling' of quicklime or salt on the ground around the plants is the usual method, but a more effective one has been recommended by a resident of Denver, Colorado. He uses a solution of ammonium sulphide (one part to thirty parts of water), which he hoses on to the plants. Nearly ail the snails and slugs in his garden were killed in a single night by this method, and the plants were not harmed by the solution. The large East African snail, Acliatina fulica, which is three inches long, ;rivals the garden snail in its ability to extend its range per medium of modern transport, and promises to become a menace throughout the tropical and subtropical world, half of which it already infests. Tiiis snail was transported along with coffee plants from East Africa to Mauritius nearly a century ago; thirty years later it was carried thence to Calcutta, and by 1910 it had become common in Northern Bengal. About 1900 it obtained a footing in Ceylon and within a little more than ten years had become a disgusting pest. From Ceylon or India to Malaya and to Singapore and so to Cl\ina mark the stages of progress, which is certainly not at an end. The snail is voracious and prolific; it lays about one hundred eggs in its first year, two to three hundred at the end of the second year, and close on a thousand in all.

Poisoned Whitewash. In 1028 it was introduced to Sarawak from Singapore as food for poultry, and by 1930 had become so great a pest that in 1931 a small reward was offered for its destruction. Hand-picking, dumping in the ocean, burying the animals in sacks deep ill the ground have all been tried with little effect as methods of control.

In Ceylon, however, a method of control for this tropical pest has been found. It was noted that the lack of lime in Ceylon caused snails to develop a passion for whitewash, for which they crawl up walls and buildings. This fact induced people to place poisoned whitewash in the areas most infected by these snails.

One cannot leave the snail without quoting a few verses of A. P. Herbert's amusing little poem on tlia snail:

The life of the snail is a fight: against odds, Though fought without fever or flummox; You see, he is one of those ga'steropuds Which have to proceed on tlieir stomachs. Just think liow'd you hate to ; go round on

Especially if it was gummy,' And whenever you travelled you left on a stone The glistening tracks of your' tummy 1 1