Spanish Slug Taken at Dunadd in the Summer of 2007 using Nikon D40X with Nikon 300 mm zoom lens. Spanish Slug. Species: Order: Family: Arion lusitanicus. Pulmonata. Arionidae. Description: Length: Food: Habitat: Feature Highly invasive slug species and is considered a pest. Leopard dots can be present on some individuals. The Spanish slug is a hermaphrodite, meaning that one single slug can start an infestation. Offspring numbering up to 100 eggs may be produced. 10 to 12 cms. Decomposting matter, such as leaves, fungus, and decaying vegetable material, but some are predators and most also eat carrion including dead of their own kind. They also feed on fruits and vegetables prior to harvest, making holes in the crop that makes it more vulnerable to disease Moist environment. In the past two decades, its mating with Arion ater. (or Black slug) has resulted in a more resilient hybrid exhibiting increased tolerance to cold. Like snails, most slugs have two pairs of 'feelers' or tentacles on their head. The upper pair—optical tentacles—are light sensors; the lower pair provides the sense of smell. Both pairs are retractable and can be regrown if lost.