Large Black slug (Arian ater)
(Arian ater)
The large black slug has its good and bad points. Hear us out please.
True, it is not the most cuddly of creatures, and gardeners detest it because of its fondness for eating fruit, vegetables and tender young plants.
But when it is not devouring our precious crops it is doing a valuable job for the ecosystem by recycling decaying plant material and helping to keep the soil nice and healthy.
The black slug grows 10 to 15cm long. Most live up to their name colour-wise but some adults are brown or even white. They breathe through holes behind their heads and move around using a single muscular foot, lubricated by trails of slime which they produce themselves. They are not fast; top speed is 4.5cm per minute.
Fascinating fact:
The black slug can produce three different sorts of slime; two to travel around on and a third to cover itself in to deter predators. This third type tastes absolutely vile, although it is hard to imagine that the other two are much better.
Black slugs are common and widespread throughout Scotland. They are most active at night but are also often seen on wet days.
They live in grasslands, woodland, hedgerows and gardens and eat almost anything: fungi, carrion, earthworms, leaves, stems, dead plant material and dung.
Black slugs have both male and female genitalia but still prefer to mate with each other. After mating, an individual slug will lay up to 150 eggs every one to three weeks from August to October, although the clutches fall in size to 20 or so late in the season.
The young take at least 27 days to hatch and nine months to mature, ready to mate in early summer of the following year. The adults die after laying their last clutch of eggs; few survive into a second year.
Despite the awful mucus mentioned above, the black slug has natural predators including the hedgehog, badger, shrew, mouse, frog, toad, carnivorous beetle, and some birds. When picked up or touched, it will roll itself into a semi-circle and rock from side to side. This defensive behaviour confuses predators and is unique in its wider slug family.
Did you know
Some slug pellets can kill other creatures besides slugs, including dogs and cats. And some experts do not recommend pellets (even organic ones) because they say they will harm other garden wildlife. If you want an alternative method of slug control, some say they are attracted to beer and porridge and put off by garlic oil.