La limace rouge - The red slug
On the 1st. September last year these two slugs were captured 'in flagrante delicto' as they say. At over 15 cm. long the bright red slugs are very obvious as they glide on mucus strands over the ground. If it were not for the colour, they would be indistinguishable from the large black slug. Some would maintain that it and the black are the same species. It would therefore be interesting if you found a black and a red slug mating. In Britain it would be unusual to find the red form which is far more common in southern areas. But I have found the black form on the stones of Montsegur château in southern France which is about as far south as it could get! Neither is found in eastern Europe or in the far south of Spain and Italy. I hestitate to suggest that the two are kept apart by distinctive ecological preferences, but you never know! The black species can be found in far more exposed places than the red. Common sense would suggest that they are distinct species. Colour variations in both make it difficult to separate the populations.
Both, as far as is known, eat almost anything from cabbages to dead crows. The mouth contains a toothed file of continuous growth that rubs away at the food and grows at one end as it grinds at the other. The mating process takes something like two hours. Since they are hermaphrodite both exchange sperm and both lay eggs. More than 100 eggs are laid together in cavities in the soil. The reproductive openings are located close to the head end and parts of the reproductive apparatus will be enveloped in the mucus swelling seen in the photo. Above this is the lung opening, the lung itself being beneath the large fold just behind the two stalked eyes. The lung fold or 'mantle' is a good guide to the various species of slug. In some it has the pattern of a thumb-print with curved lines impressed upon it. In other species it is just granulated without a pattern, as is the case in the red (and black) slug. Behind the mantle there is only solid muscle and no 'vital' organs.
A peculiar characteristic in both species is that the animal will contract itself into a tight hunched knob when disturbed and then, if you annoy it, will rock gently from side to side.