Black Slug – Arion ater Group

Another set of species that don’t readily want to identify themselves. The Arion ater Group is so named as there are four species which are so similar as to require dissection to determine to which any one specimen may belong. These species are:

Arion ater, Arion rufus, Arion vulgaris and a fourth species yet to be described. In all likelihood we have probably recorded two or more of these species but for now will just refer to them all as part of this grouping.

If the ground is wet and its not too cold we often see lots of these guys out and about chomping on a variety of vegetable matter. This fella was very content and didn’t appear to mind my fussing around him with the camera at all….

We already knew these guys ate more than just vegetable matter as we have seen them on several occasions munching on ‘that what the dog leaves behind’, but apparently they also will eat dead animals and even attack earthworms (not something we have ever witnessed).

Of course they don’t get their own way all the time and we have often seen birds, especially blackbirds, hopping around the grass following rain, picking up several slugs in one go. Toads are also known to feed on slugs, which we have lots of in the garden.

These guys are hermaphrodites, but different sources conflict on whether or not they can self-fertilise. In any case we know they do like to get together and exchange sperm on occasion, in the case below just between two individuals but they can often be found doing so in larger groups.

In our garden we don’t see these guys as any sort of pest or see them in massive numbers. They are of course good for helping break down leaf litter and other decaying matter in much the same way as earthworms do. This helps bacteria and fungi finish the job of recycling nutrients in the soil.

Red Form

Black Form

So for now we are happy to have these guys about.

DC 29/12/2021