Description: One of the 'garden' slugs characterised collectively by their depressed, relatively elongate shape, inability to contract into a bell shape, and orange sole. The present species is distinguished by the colour of its sides below the lateral bands, which are whitish grey to a bluish grey, by its tentacles which have a warm, rosy flush and by the absence of orange colour on the back. 30-35 mm.

World Distribution: Found across north-west Europe including the British Isles, France, Holland and Belgium, but not extending as far north as Arion distinctus, nor as far south. Distribution type: Oceanic Temperate (71).

Irish Distribution: Mainly recorded from southern and eastern counties becoming steadily rarer towards the north and west. In northern counties generally confined to gardens or on well-drained soils, particularly near the coast.

Ecology:

• In southern counties it tends to outnumber Arion distinctus in woodlands but the seasonality is different
• Davies (1979) considered that A. hortensis was more closely associated with gardens than A. distinctus but there is in fact little ecological separation in Ireland; De Wilde (1983, 1986) found a similar lack of separation in Belgium
• Arion distinctus is more tolerant of cold, moisture-saturated soils and its European range extends farther north, to Scandinavia and the Faroe Islands (Holyoak & Seddon, 1983)
• An autumn breeder with adults more likely to be present in summer and autumn

Key Identification Features:

• A garden slug with depressed elongate shape and inability to contract into a bell shape
• Colour generally dark, but with more contrasting, whitish sides and dark back, and bright orange or orange-red sole
• Tentacles dark grey but translucent, with a warm or rosy glow
• Back colour always uniformly grey without the paler shades found in many Arion distinctus in which orange chromatophores tend to accumulate on the back
• Tuberculation on the back slightly better developed than in A. distinctus with more elevated tubercles, apparent more when at rest

Taxonomy:

• See remarks under Arion distinctus.

Red list status:

• Least concern (lc).

Distribution Map from NBN: Arion hortensis at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Arion hortensis at iNaturalist World Species Observations database.

GBIF data for Arion hortensis | Classification: Gastropoda, Stylommatophora, Arionidae, Arion

Thumbnails for genus Arion