dusky slug

(Arion subfuscus/fuscus)

Conservation Status
dusky slug
Photo by Alfredo Colon
  IUCN Red List

LC - Least Concern


NNA - Not applicable


not listed


Dusky slug is a common, exotic, terrestrial, round back slug. It is native to northern Europe and was introduced into North America. It was first reported in the United States in the vicinity of Boston in 1842, and by 1940 it was widespread across North America. Molecular DNA evidence suggests that it probably came from Britain, France, or the Netherlands. It was likely introduced several times. It is found in moist or wet areas in deciduous and coniferous woodlands, in meadows on rocks, and in old fields and waste places. It is often encountered in areas of human activity, including in roadsides, gardens, campgrounds, wood piles, and window wells. In natural areas it is sometimes more abundant than native snail and slug species. It can a pest of agricultural crops, forest replantings, and gardens.

Two species of dusky slug are often treated as a single species complex, a group of species so similar that the boundaries are unclear. Western dusky slug (Arion subfuscus) is native to western Europe, northern dusky slug (Arion fuscus) is native to central, eastern, and northern Europe. Aside from their geographic distribution, the two species can only be distinguished by the size and color of the genitalia of dissected individuals, or by analysis of their alloenzymes. Both species have been introduced into North America.

The adult is 2 to 2¾ (5 to 7 cm) long. There is no shell. The body is long and slender when extended, short and bell-shaped when contracted. It is not keeled, and it does not have an elevated hump. The back plate (mantle) is about one third the total length of the body. It is covered with rows of pale bumps (tubercles), giving it a finely granular appearance. It is variable in color, but populations generally fit into one of four color groups: blackish-brown, yellowish-brown, orange, and reddish-brown. The orange or yellowish-orange color is mostly – or completely – due to a covering of mucus. When handled, the mucus will stain the handler’s fingers. There is usually an indistinct brown stripe and a lighter region above the stripe on each side extending the entire length of the body, but this is sometimes absent. The area near the foot fringe is whitish. The underside (sole) is pale yellow. It is not divided buy two longitudinal furrows. The head and tentacles are black.




2 to 2¾ (5 to 7 cm) long


Similar Species


Deciduous and coniferous woodlands, meadows, old fields, waste places, roadsides, gardens, campgrounds, wood piles, and window wells.




Summer and fall






Life Cycle






Mushrooms, living and dead plant matter, fruit, and animal excrement.


Distribution Map



24, 29, 30, 83.





  Class Gastropoda (gastropods)  
  Subclass Heterobranchia (heterobranch gastropods)  
  Infraclass Euthyneura (euthyneuran gastropods)  
  Subterclass Tectipleura  
  Superorder Eupulmonata  
  Order Stylommatophora (common land snails and slugs)  


Helicina (helicinan snails and slugs)  
  Infraorder Arionoidei  


Arionoidea (roundback slugs and allies)  


Arionidae (roundback slugs)  
  Genus Arion (arion slugs)  



Subordinate Taxa


northern dusky slug (Arion fuscus)

western dusky slug (Arion subfuscus)




Limax fuscus


Common Names


dusky arion

dusky slug












On gastropods: the fleshy, membranous covering of the front of the body.






Visitor Photos

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Alfredo Colon

    dusky slug      
    dusky slug   dusky slug  

Greg Watson

    dusky slug      
MinnesotaSeasons.com Photos





Dusky Slug (Arion subfuscus)
Andree Reno Sanborn
  Dusky Slug (Arion subfuscus)  
Arion subfuscus
Lloyd Davies
  Arion subfuscus  

Arion subfuscus




Visitor Videos

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Other Videos
  estern Dusky Slug (Arion Subfuscus) During a Thunderstorm
Cool Nature Clips

May 19, 2022

  Arion subfuscus (Draparnaud, 1805) Dusky Arion Slug
Chin Frank

May 15, 2014

From garden in residential area, Eugene, Lane County, Oregon, May, 2014. See: https://jacksonvilleshells.org/416tts.htm




Visitor Sightings

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  Greg Watson

Location: Eagles Bluff Park

dusky slug  
  Alfredo Colon

Location: Albany, NY

dusky slug  
  Alfredo Colon

Location: Albany, NY

dusky slug  
  Alfredo Colon

Location: Albany, NY

dusky slug  
MinnesotaSeasons.com Sightings






Created: 11/19/2022

Last Updated:

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