A Comprehensive Study of the Roman Snail
by Michael Ratsey
 

Adult snails start to hibernate in late October, emerge in late March and April (Photographs 3 & 4) and start pairing from May onwards to lay eggs when and where the soil is damp from June through to early September. Juveniles hibernate slightly later and emerge slightly earlier.

Most activity; feeding, movement and pairing occurs on mild nights and when the ground and atmosphere are damp. On really warm wet nights an adult snail will readily cross a fifteen metre lawn.



Roman Snails - Helix Pomatia (Linné/Linnaeus, 1758)

The Roman, Pot Lid or Apple Snail is the largest of our native and N.W European land snail species, 30-50 x 32-50mm, and is familiar to many as a delicacy in France commonly known as l’escargot.


The ground colour of the globular shell is a creamy tint, turning white with age, and upon it from three to five spiral bands usually of pale brown. The surface is not as smooth as the more common garden snail, Helix aspersa, and the lines of growth more distinctly raised. There are five convex whorls and the shell mouth is nearly round with a thickened slightly pigmented lip. The umbilicus is very small.


The fact the species is restricted in range to a few calcareous southern English counties, and its local occurrence even there, has perpetuated a wide belief in the legend that it is not indigenous, but was introduced by the Romans (AD 43 – 410) – hence the name. Other theorists have placed the date of its supposed introduction to the sixteenth century, although the Pro-Romanists point to a number of acknowledged sites of Roman settlements and villas in whose neighbourhood the snail is found. There are plenty of places where there are vestiges of Roman civilisation where no snails are found at all. The stronghold for this species in UK is the Downs in Buckinghamshire.


The name Pot-lid snail comes from the Greek pomma; the reference here being to the solid chalky epiphragm with which it closes the mouth of its shell before hibernation. When the time comes for its winter rest the snail seeks the shelter of undergrowth, and there burrows down beneath the leaves and into the earth below.

With its slime it unites some of the vegetation debris to form a roof, and then manoeuvring its shell so the aperture is uppermost, it constructs the thick epriphragm which is sufficiently robust to be able to remain exposed and undissolved for at least five winters. Unlike most snails which leave an air-hole in their epiphragm, Helix pomatia has a porous pot-lid rather similar to hard Plaster of Paris. (Photographs 1 & 2)

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If the climate is dry they become inactive and aestivate, which they often do by burying just below ground surface, (Photograph 5) although unlike during hibernation, the shell aperture faces downwards.

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Mating is an unusual process; the participants circle each other and then raise the front part of their bodies and press their soles against each other. (Photograph 6 - 8)

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Occasionally if the mating becomes frenzied a calcareous love dart may be ejected by one or both snails and embedded in the flesh of the partner. (Photograph 9) Multiple orgies can also occur. (Photograph 10)

They are hermaphrodite and both snails simultaneously fertilise. Mating can take up to twenty-four hours.

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Egg-laying occurs in the soil. The snail burrows head first to a depth of between 4 – 5 centimetres so only the spiral part of the shell is visible from the surface. A cavity is excavated to hold however many eggs will be laid; each one being a bit more than a millimetre in diameter. (Photograph 11) Egg numbers recorded in the wild varied between 10 and 40 by Edward Step in 1945, although this can be exceeded considerably.

Similarly to tortoises the eggs are chalky white and irregularly roundish in form. They hatch within 20 to 40 days depending on the temperature and the snail-chicks eat their egg shell in the same manner as newly hatched caterpillars. (Photograph 12)

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Darwin recorded in his Descent of Man some evidence of intelligence, communication and homing instinct among Helix pomatia. Life expectancy can exceed 8 years.


They are easily reared in captivity, if time is prepared to be spent on regular feeding, cleaning of housing containers and checking for and the removal of parasites.


In England only (not the rest of the UK) the Roman snail is a protected species under the Wildlife and Countryside Act 1981, making it illegal to kill, injure, collect or sell Roman snails.

The snail was placed on the IUCN ‘red list’ of threatened and endangered species in January 2009.