Spanish slug

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Spanish slug

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Order:	Pulmonata
Family:	Arionidae
Genus:	Arion
Species:	A. lusitanicus

Binomial name

Arion lusitanicus
(Mabille, 1868)

The Spanish slug, more commonly known in English-speaking countries under its Latin name, Arion lusitanicus, is a highly invasive slug species that is often considered a pest in areas where it is not indigenous, and often in places where it is.

The species originates from the Iberian Peninsula, although it is noticed far more often in northern parts of Europe, where it was first discovered in the mid-1900s. The animal is about the same size as its relative, the black slug, growing to a maximum size of about 12 cm. Leopard dots are a characteristic feature, albeit not present among all individuals.

A Spanish slug eating clover

The local name of the slug in the regions it has invaded is typically a translation of "Spanish slug." In recent years, as its dominance has increased, it has been nicknamed "killer slug", perhaps due to its tendency to eat dead or weaker individuals of the species, although its destructive impact on gardens may seem just as appropriate a reason for the name.

The main reason behind problematic invasions of gardens by the Spanish slug is that it is a hermaphrodite, meaning that one single slug can start an infestation. Offspring numbering up to 100 eggs may be produced. Bad export control may also be a cause, as the main route for the slugs to spread is through careless handling of imported produce from Spain and Portugal.

In recent years, it has been found that the Spanish slug has bred with the indigenous black slug to produce a more frost-resistant variety in more northerly regions.