MolluscIreland - land and freshwater
  • Arion (Kobeltia) hortensis A. Férussac 1819 Southern garden slug
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Arion (Kobeltia) hortensis
© Dr Roy Anderson
Arion (Kobeltia) hortensis
© Dr Roy Anderson
Arion (Kobeltia) hortensis
© Dr Roy Anderson

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Arion (Kobeltia) hortensis
© Dr Roy Anderson
 

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.

Key characteristics

  • 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

Size

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 A. 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

Taxonomy

See remarks under Arion distinctus.

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Arion hortensis

 Anderson, R., (2016). Arion (Kobeltia) hortensis A. Férussac 1819. [In] MolluscIreland.
http://www.habitas.org.uk/molluscireland/species.asp?ID=31 Accessed on 2017-04-27.