Slugs

The European Black Slug (Arion ater) is native to Europe and was introduced to North America. It can become a garden pest in both places but we must not forget that it is a very useful member of natural ecosystems when it is in its natural woodland habitat.

Garden Pest

The Black Slug likes gardens. It is very fond of many of the plants that humans grow but it is not usually the most serious slug pest. It is true that it will sometimes eat your crops and become a nuisance, but it prefers a rather more unsavoury foodstuff and that can make it a useful member of the garden community.

Eater of Faeces

Black Slugs seem to like eating cat and dog faeces, and these are turned into slug faeces which are much more acceptable in the garden! It is also fond of rotting vegetation and fungi so, on balance, it is probably a garden ally rather than a foe. Much of its time is spent usefully recycling waste matter and thereby improving soil quality, and for this we should probably allow it the occasional lettuce?

Black and Orange Varieties

There are many colour varieties of the ‘black’ slug. It can be black or almost white, or various shades of brown through to orange. There is still a debate about this orange variety – is it a separate species (Arion rufus), a subspecies (Arion ater rufus) or simply yet another colour variety of Arion ater? The orange ‘variety’ does seem to have a slightly different internal anatomy, but the final decision will probably have to wait until the genetics of this species is better understood.

Mating Habits

Slugs, like snails, are hermaphrodites and the Black Slug is no exception. They twine in pairs on damp evenings and fertilise one-another. The eggs are laid in a sheltered position and the young take about a year to reach maturity. Another species of slug, (Ariolimax dolichophallus), a species of American banana slug, is remarkable in that it has the largest penis in the world (for its size) up to five times the body length! This can be a problem when copulation is over, and this species is one of several that have arrived at an unusual solution. When copulation is over they will often bite off their own, and/or, their partner’s penis! After this operation they become female. Why this type of slug has become the mascot of the University of California since 1986 is baffling – maybe it is because some students run around naked when it first rains – or maybe there are other reasons?

(you can click on the images below to enlarge them and see the whole photo)

Other articles by John Blatchford

Large Black Slug

Slug and Snail

Slug Feeding

Pale Form

Orange Form

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