Black Slug Taken at Pow Burn on 26th May 2019 using Panasonic Lumix LX5 in macro mode. Taken at Achnabreck in the Summer of 2007 using Nikon D40X with Nikon 300 mm zoom lens. Black Slug. Species: Order: Family: Local Names: Arion ater. Pulmonata. Arionidae. Description: Length: Food: Habitat: Feature Like all other species of the Arionidae family, the black slug is a hermaphrodite, meaning it can fertilize itself if needed, although a mate is preferred. After mating, the slug lays eggs about 5 mm in diameter.The favoured location for eggs is a dark, cold, damp place such as a compost heap. 10 - 15 cms. Decomposting matter, such as leaves, fungus, decaying vegetable material and carrion. Moist environment. In the past two decades, it's mating with Arion lusitanicus (or Spanish 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.