MolluscIreland - land and freshwater
  • Arion (Mesarion) subfuscus (Draparnaud 1805) Dusky slug
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Arion (Mesarion) subfuscus
© Dr Roy Anderson
Arion (Mesarion) subfuscus
© Dr Roy Anderson
Arion (Mesarion) subfuscus
© Dr Roy Anderson

Map hosted by the National Biodiversity Data Centre, Waterford
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Arion (Mesarion) subfuscus
© Dr Roy Anderson
Arion (Mesarion) subfuscus
© Dr Roy Anderson

A medium-sized, dusky brown to orange roundback slug distinguished from other, similar species and their young by the very flat tuberculation on the back and by its inability to assume a bell shape when fully contracted. Common in woods and on wild ground but not in gardens.

Key characteristics

  • A medium-sized roundback slug of a predominantly brown colour, ranging from black-brown through olive-brown to orange, occasionally a bright reddish-orange
  • Lateral bands nearly always present and of a slightly to moderately darker shade than the rest of the upper surface
  • Foot fringe pale with thin lineolations (less well formed than the large roundback species)
  • Sole uniformly pale, slightly translucent
  • Tentacles pale
  • Exhibits no rocking response and is unable to contract into a bell shape when stimulated


50-70 mm.

World Distribution

Throughout Europe but commonest in the west. Distribution type: European Wide-temperate (63).

GBIF distribution map [open in new tab]

Irish Distribution

The second most common Irish slug after Deroceras reticulatum.


  • Ubiquitous and abundant in all categories of land, except gardens, to the summits of high mountains including Slieve Donard, Co. Down (850m)
  • Commonest in woodland where it hides under stones and dead wood

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Arion subfuscus

 Anderson, R., (2016). Arion (Mesarion) subfuscus (Draparnaud 1805). [In] MolluscIreland. Accessed on 2024-03-02.