Arion hortensis/distinctus

Arion hortensis on a leaf

Biological Name

Arion hortensis Férussac, 1819; Arion distinctus Mabille, 1868

Common Name

Garden slugs

Other Common Names

Black field slugs, darkface arions

Appearance/Characteristics

Small slugs, 25 to 35 mm body length, a keel is absent. The pneumostome on the right side of the mantle is located in the anterior half oft the mantle.

Body with a bluish grey colour and dark lateral bands, the back is almost black. The foot sole is orange or yellow, the mucus is yellowish.

Other Similar Species

Arion silvaticus, Arion owenii

Biological Notes

Both species belong to a species complex which includes several, partly unknown species. They are annual species, live mainly subterranean and have overlapping generations. A big proportion of adults is present in winter time.

Geographic Distribution

Garden slugs are among the most commonest and most widely spread slug species. The distribution areas of the two species overlap partly, but Arion distinctus has a broader distribution area. It covers western and central Europe and has been introduced to Northern America.

Habitat

The two species of garden slugs can be found in human-made habitats as gardens and cultivated fields but also in urban areas, bush habitats and deciduous forests. They live in the leaf litter or in crevices in the ground.

Crops at Risk

Horticultural crops in humid climates, mainly tubers or strawberries and seedlings of brassica. In mild winters garden slugs can be responsible for the underground loss of autumn sown winter wheat by hollowed grains.

Damage Caused/Symptoms

Feeding on tubers and seedlings, hollowing seeds.

Impact and Severity

Seedlings and young plants can be severely damaged, as the slugs show high activity during springtime. Later in the year, root crops, such as beets and carrots can be damaged by eating holes and leading to bacterial rotting.

Prevention and Control

Garden slug densities are not easy to estimate, as they live hidden in the ground and live nocturnal. A method of prevention is to reduce the favourable habitats where Garden slugs live and reproduce, i.e., disturbing the soil by tillage reduces garden slug abundance.

Natural Predators

Garden slugs are eaten by ground beetles and their larvae, as well as by some bird species.