Arion hortensis group: Arion distinctus




Arion distinctus Mabille, 1868

Common Name

Dark-face arion


This slug belongs to a species-complex called the Arion hortensis group, which is comprised of Arion hortensis, A. owenii and A. distinctus. The Arion hortensis group is typically 25-35 mm long, and is only distinguished by the morphology of the genitalia. These slugs have two color morphs (dark grey or bluish grey ) that are more common than the brownish morph. They possess dark lateral stripes, where the stripe on the right side of the animal encompasses the pneumostome (breathing pore). Like the body, the tentacles are bluish grey with a contrasting pale yellow or orange sole. The animals have no keel. Contracted specimens are rounded in cross-section. This group has a characteristic yellow-orange mucus. Molecular techniques can also be used to identify members of this group.

Genitalic characters used to distinguish the three species:

Arion distinctus: epiphallic structure conical in cross-section, and covers the entire opening of the epiphallus.

Arion hortensis: epiphallic structure raised with "finger-like" projections, and only partially covers the opening of the epiphallus.

Arion owenii: epiphallic structure flattened and irregularly shaped, and does not cover the opening of the epiphallus.

Native Range

Western Europe


North America:

  • U.S.: California, Pennsylvania
  • Canada: Vancouver, Southern Vancouver Island, Halifax, near Ottawa and Kingston

Australasia: New Zealand



This slug consumes agriculturally important crops and often inhabit disturbed sites (e.g., gardens, roadsides). Arion hortensis and A. distinctus reproduce by cross fertilization. The means by which A. owenii reproduces has not been documented. In England, A. hortensis mates in the fall and winter while A. distinctus mates during spring and summer months. They can live up to one year.


  • Arion hortensis of authors in part, not Férussac, 1819
  • A. hortensis form 'A' of authors.


Davies 1977; Davies 1979; Grimm et al. 2009; Horsák 2004; Hunter 1966; Iglesias and Speiser 2001; Kantor et al. 2009; Roth and Sadeghian 2006

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