There are various reasons why the conchologist tries to rear snails, apart from that of studying their life histories. The genetics of polymorphic species such as Cepea hortensis can only be studied by means of breeding experiments. Young snails often look very different from the adults, so it is of great assistance in field work to be able to recognise them. If a species is scarce, breeding provides a means of obtaining a good cabinet series with¬out endangering a local population, and sometimes interesting varieties may turn up; also, to have 100 or so snails of known age is very convenient if one is investigating their anatomy and development.
Sometimes snails are found in the act of egg-laying in the field. This is a great time-saver, as they can be placed in an observation nest at once. The eggs are usually laid in a compact mass in a cavity just below the soil surface, and these conditions have to be imitated. A 2-inch- deep glass specimen tube is one quarter filled with the local soil of the same moisture content as that next to the eggs, and lightly pressed down with a finger. The egg mass is then gently rolled into the tube (preferably with a teaspoon, a most useful piece of collecting equipment) and covered with a tuft of damp moss, surface litter, or a little more soil. A number is attached to the tube, corresponding to an entry in the notebook, and thereafter the firmly corked tube should be kept upright and shaded from the sun. The eggs can be inspected daily through the glass. Eggs laid by captive snails in boxes should be treated in the same way.
Snails will usually lay eggs in captivity if one is patient enough. A specimen of Helicella virgata from Tripoli waited 18 months for a mate from the same locality before laying, but usually the wait is only a few weeks or days. Adult or sub-mature specimens are put into jam jars containing an inch or two of damp soil, preferably mixed with crushed chalk, and covered with a perforated lid. Food is most conveniently provided by slices of potato and cabbage, skewered on a stick for easy removal. Rolled oats are unsuitable for use in jars, as they soon decay and are difficult to remove. If the soil dries out too much a little water is poured in and allowed to percolate through the soil, but as this is easily overdone it is wise to set the limit at two teaspoonfuls. Provided the soil is not too deep the eggs can be seen through the bottom, lying on the glass, and can be inspected every day. With luck, the nest will be formed at the side and the whole operation can be watched. It usually takes place at night, and is a lengthy process. The snail must be removed as soon as it has closed the nest. It is unwise to keep more than one species or 2 or 3 individuals in the same jar.
Eggs are best kept in the dark at ordinary room temperature, except those of tropical species, such as the Achatina, whose eggs have just hatched in my greenhouse at day temperatures of 85 Farenheit.
Hatching generally takes place in from 15 to 21 days, but some species take longer. The babies eat their eggshells, and this unpromis¬ing diet lasts them about 5 days, during which they remain in the nest. Then they dig their way to the surface and are seen crawling about the soil and glass. They should be left where they are for a few days, as they sometimes like to return to the nest to rest. If they are in corked tubes it is advisable to replace the cork with a plug of cotton wool. At this stage they will eat a little finely shredded cabbage dusted with rolled oats.
Baby snails are very sensitive, and in captivity have 3 main enemies: dryness, excess wetness, and mould. Of these the wetness is the most dangerous, causing drops of condensation to form, in which the babies are trapped and drowned. Most of my earlier attempts at rearing failed through this cause. The best safeguard is adequate ventilation, but this nan lead to an almost equally dangerous drought. It is essential, therefore, to provide conditions of uniform humidity without excess wetness, and for this there is nothing to beat the transparent plastic sandwich box. A convenient size is one 7" x 4.5" x 1.5" deep. A hole about 1" wide is cut out of the centre of the lid with a hot poker, and the rough edges smoothed with a file; then, by means of a modern glue such as "Bostik", a piece of perforated zinc is fitted over the hole. The perforations are quite wide enough to allow the escape of a baby snail, but they never attempt to get out as they hate walking on the zinc. A thin layer of damp soil is placed on the bottom of the box, sprinkled with crushed chalk, and pressed down. On this is placed a piece of tender cabbage leaf, concave side downwards, and a little powdered rolled oats dusted over the leaf. A box set up like this stays healthy for a month at 60°F.
The next problem is the transference of the baby snails to the box. They are too fragile to handle, but if the uncorked tube is laid in the box they will all crawl out in a few days and the tube can be removed. If they have hatched in a jar they should be all right for a few weeks if fed carefully, but sooner or later will have to be moved. For this, a squirrel hair paint brush and a teaspoon are used, in the same way as a dustpan and broom. Great care must be exercisedi Another method is to replace the top of the jar with a piece of cardboard with a hole in it, and invert another jar containing a few leafy twigs on top. In a few days they will all have crawled up into the leaves, which can be picked off and placed in the rearing box.
Mould is avoided by good ventilation and the removal of any uneaten food every two days, but it is better to avoid over-feeding. Experience is the only guide in this. Sometimes the soil becomes infested with springtails, mites, or small white worms. These are harmless, but indicate dirty conditions, so the babies should be moved to a clean box and the dirty one washed out with hot water.
For most snails the best diet is a mixture of rolled oats and fresh green leaves. Lettuce "goes off" too quickly, and cabbage, though excellent, sometimes gives rise to unpleasant smells. The best thing is to give them a mixture of leaves, the most popular being hollyhocks, clover, dahlia, hogweed and enchanter's nightshade. Soft young leaves should be avoided as they tend to shrivel up, enclosing the babies in a fatal grip. An occasional change of diet keeps them feeding well. They love hay in any form, e.g. dead herbaceous stems, grass hay, and leaves of elm, sycamore, etc., collected, washed, and dried as they fall in the autumn. These materials need to be dampened before use, and should be removed when the snails appear to lose interest. Small woodland snails usually eat leafmould, but welcome a tuft of moss or lichen. The average snail tends to be rather omnivorous, appreciating a little animal food in the form of a very small amount of dried shrimp fish food, mixed into the rolled oats.
It is astonishing how much chalk a snail family can consume in one week. Common chalk from a roadside pit is best, but limestone chippings, old mortar, or crushed oyster shells will do at a pinch. They take it as a powder sprinkled on the food, but prefer it in small lumps the size of peas, scatter¬ed on the soil. Without a good supply they cannot make strong shells, a -57~ factor of some importance when handling them.
The babies should be all right in their plastic boxes for a month, by which time they will need larger quarters. A very serviceable vivarium can be constructed from wood. A good size is 1 ft. long x 6" wide, with a glass top sloping down from a 6" back to a front. The ends are better if square, as this allows several to be stacked on top of each other to save space. The slope of the glass throws off condensation, which soaks into the wood. The glass rests on narrow quarter-round beading, and must fit snugly to prevent accidents. Two 1" holes bored in the front to admit air are covered with perforated zinc, tacked to the inside to avoid the formation of hiding-holes from which the inhabitants are difficult to extract. The wood needs to be at least ij" thick, as it must resist decay without the aid of any paint or preservatives.
A vivarium of this type should be set up in the same way as the plastic boxes, with damp soil, chalk, leaves, etc., but with a greater depth of soil to hold moisture. The snails are transferred to the box with a teaspoon, and examined and fed at least twice a week until they have grown to a size at which they seem better able to take care of themselves; after which they can be neglected for a week at a time if necessary. However, if they are growing very quickly they may need daily attention. Uneaten food must be removed before it decays, for although snails love dead vegetation they are soon upset by mouldy food, and begin to die off.
Wooden boxes dry out more quickly than plastic ones, so an occasional spraying with tap water, (unless heavily chlorinated), is desirable. However, there is much to be learned about this, and one should consider the natural habitat. For instance, all my attempts at rearing Theba pisana failed, until I discovered a clutch of young ones thriving in a bone-dry box in which a number of adults were aestivating, an obvious case of a species having a low optimum humidity. It reminded me of a colony of Helicella itala I once knew, living on heavily grazed turf around rabbit burrows. When myxomatosis destroyed the rabbits the grass grew up tall, and in the more humid conditions the italas all died out.
Whatever snails are kept, it is a good idea to give them a good supply of leaves, dead or alive, as this, paradoxically, gives them more "space". They do not worry much about the volume of the box, but they do need a large surface to crawl on, which the leaves provide. Also, they help to maintain a moist atmosphere, and it saves having to change the soil too often.
The rate of growth varies with both species and individuals. For example, a young achatina of mine has grown less than one whorl in a year, whereas 40 Helicella obvia have come from the egg to nearly full growth in half that time. As is usual in any population, some individuals grow faster or slower, maturing at different ages, but the very slow ones are mostly "runts" and never make much progress, a few dying each month until about 15 or 20 per cent of the family have perished. Ideally, snails should be kept growing as steadily as possible, as occasional short spurts of growth under artificial conditions lead to lumpy, distorted shells and small ultimate size. To achieve even growth takes practice, but there are some useful hints to be gleaned from their behaviour. Snails, like many animals get "bored", and respond by going to sleep. Even when fresh food and a sprinkle of water are given, they scarcely move. The remedy is to remove them to another box. It can be identical with the one they have just left, but provided they have some fresh soil as well, they will take on a new lease of life.
Boredom, however, should not be confused with aestivation. This seems to be the result of high temperatures, and even if awakened by a cold shower they soon seal themselves up again. Mostly they aestivate on the sides and top of the box, but sometimes they bury themselves in the soil. The best guide as to whether they are truly aestivating is to find out whether their sleep coincides with the dry season in their country of origin; thus I find that Mediterranean snails sleep for 2 to 3 months in our summer, and Kenyan snails sleep in our winter, regardless of the degrees of temperature and humidity. It is best to let them have their own way, perhaps giving them a showerbath once every 2 or 3 weeks until they wake up properly.
No matter how fast the snails grow they do not usually mature until their second season, often at a set time. For example Helicella virgata matures in the autumn, but (as far as my observations show) Eobania vermiculata matures in the spring. They may reach full growth, but the thickening of the peristome seems to be delayed until the appropriate season.
When rearing foreign species, always burn the old food and sterilize the soil. You don't want to introduce an alien which may become a pest, like the rabbit in Australia.
M. R. Block