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A Spotted Cellar Guest

© Esther Wullschleger

For many Europeans living on the countryside, a browny spotted slug is a common sight in the garden during summer evenings. This fairly variable snail, normally colored irregularly with dark stripes or dots along the body, originates most probably from southwestern Europe. It has accompanied humans through large parts of Europe and even overseas, spreading also to Australia, North and South America as well as Hawaii. Americans know this unwanted immigrant as the giant garden slug, the great grey slug or the spotted garden slug, while Australians usually call it leopard slug. While local names may vary, the slug is unmistakably characterized by its scientific name, Limax maximus.

Originally, Limax maximus was living in forests, where it was feeding mainly on decaying material on the forest ground. But, above all in its newly acquired habitat ranges, it does now also live quite commonly in areas settled by humans. There, it appears to have a special preference for humid cellars, and some people mentioned that these snails might eat not only plants in the garden, but also stored food in the cellar (it is said to especially like tomatoes and mushrooms). Pet food that is left unattended certainly attracts them.

As indicated by the name, Limax "maximus" can reach considerable sizes. Adult animals can reach lengths of allegedly up to twenty centimetres. Usually, however, they are about ten centimetres long, which is still quite remarkable. Their appearance is rather slender when the animal is stretched. In Switzerland, and also in Britain, this slug is fairly common but has a scattered distribution, avoiding especially higher altitudes.

The mating behavior of these hermaphroditic slugs is particularly extraordinary: Two individuals which decide to mate climb to some elevated place, for example in a bush or in a tree. After following each other around in a circle for as long as two and a half hours, the two animals entwine and drop from the perch, hanging suspended by a tough mucus strand that may be as long as 25 centimetres. While entwined, each snail everts its penis to its full length of another 10 centimetres, and the mutual exchange of spermatozoa occurs while these penises are wrapped around each other. Both slugs will later lay a clutch of transparent eggs on moist ground under stones or other objects. While developing, these eggs gradually become more cloudy.

There are contradicting statements on the role of spotted garden slugs as a nuisance, because they are in fact omnivorous and thus eating all kinds of things. Possibly, the harm they cause in gardens varies among regions, since the slugs meet different living conditions in different parts of the world. Limax maximus might well take plants, but it equally feeds on fungi and decaying matter - or even on other small animals, which makes it a potential predator to some other garden pests. For example, it might attack other, more harmful slug species.

Limax maximus, eating on a mushroom

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