Invasion of the Spanish Slugs

[Robert Nordsieck]

Hallo everybody,

just returned from a lecture journey in Germany and full of good news...

The snail farm in Nersingen near Neu-Ulm is afflicted by an invasion of Spanish slugs (Arion lusitanicus), which IMHO, behave somewhat untypical: First the adults are still active in December, but should be dead already (shouldn't they die in autumn, as Arion lusitanicus is an annual species?!), and then they actively hunt for snails kept in that farm.

That means that sometimes several slugs attack one snail beginning at its "neck" and feeding at it from inside, eating the foot last.

The empty shell is then used to lay the eggs. The slugs not only eat the snails, they also hunt them into the neighbouring pens, when snails are brought there to be safe!

I show two pictures in the attachment, a short page concerning this problem has also already been written. However, I am still trying to find an explanation. Perhaps you can help?


> The invasion of the Spanish Slug.





Kind regards
Robert

[Rachel]

its possible they were introduced into the farm on purpose for some reason. That species is notouriously difficult to get rid of, do they have an estimite of numbers in the farm?

[Arno]

I can't see it being introduced in a snailfarm on purpose......Maybe one explanation can be that,because slugs are opportunists,they adapted their behaviour to their surroundings.
I've seen slugs crawl around here in the wintermonths,don't know if it has something to do with the winters getting milder(in general).

[Rachel]

i meant it might be because of opposition in the form of other snail farms, or people who think it is wrong.

[Robert Nordsieck]

Hi there,

it could be quite possible, that someone introduced the Spanish slugs, as there is some opposition, from other snail farms as well as from people opposed against snail farms as such.

But the phenomenon obviously appeared in several different snail farms, which makes it rather improbable, that there is some intention behind it.

Does anyone know, if Arion lusitanicus usually IS an annual species?

Kind regards
Robert

[whodoesntlovesnails]

not to be a total downer, but these slugs need to eat as well. not to say that i like seeing this, but i guess it is nature, unless these slugs were never native and now (already introduced in germany) are causing damage to the native animals.

-miley

[apple]

Arion lusitanicus are spanish slugs??
Well, these slugs are native also from here ( lusitanicus or lusitanica means « portugal») and they are prolific, but I never saw a plague of them ( maybe because they have some natural enemies).
Robert, regarding your question: They live for more than 1 year, usually. At least here.

[Robert Nordsieck]

Dear apple,

thank you very much for the correction! You are absolutely right, in the meantime I also did some research on the name. In German the species is called Spanische Wegschnecke which means Spanish slug. But of course it was stupid to simply translate it without backchecking. I found the English names Durham slug or Lusitanian slug for Arion lusitanicus. In Falkner (1990) "Weichtiere" it also says the species originated from the Western Iberian peninsula, which should mean Portugal.

On the other hand, I heard, that there is a different species endemic to Portugal, which is called Arion lusitanicus, so the species, that spread over almost all of Europe, which is another one, should rather be called Arion vulgaris, the common slug. This doubtlessly would be an adequate name, as this slug is absolutely everywhere...

To answer whodoesntlovesnails: Of course slugs need to eat as well. The question behind my posting was rather, why those slugs behave so different and much more in direction of carnivorous behaviour. There is sufficient food available (as I wrote on the respective page), so why the change? And has anybody seen this anywhere else?

Kind regards
Robert

[helikulo]

I don't know much abt slugs but I have a book about snails ('Les escargots' by Marasco & Murciano) which says slugs are carnivorous. Also here in Limoges, slugs seem to have been active right through the winter. Maybe because of the clement temperatures.