Bourguignat's Slug - Arion fasciatus

Alternative names
Rusty False-keeled Slug

Up to 35-45mm when extended. The back is grey to yellow-brown and it has a dark lateral band high up the body. The sole is pale, almost white, and the mucus is colourless. There is often a yellowish flush between the lateral stripe and the sole but this isn't always visible. Usually there is a pale 'false keel' along the ridge of the back.

Similar Species

Arion fasciatus is closely related to Arion circumscriptus and Arion sylvaticus but both these species are more grey than brown (though both also have a false keel). Arion subfuscus is generally a richer orange and also has yellow-orange mucus. Arion distinctus and Arion hortensis have a yellow sole.

Identification difficulty
ID guidance
  • medium sized (35-45mm)
  • false keel
  • yellow-brown back
  • pale sole and colourless mucus

Often in disturbed habitats such as roadsides, wasteland and gardens but can be found in woodland and scrub.

When to see it

All year.

Life History

The yellow flush on the sides appears to be influenced by diet.

UK Status

Widespread and relatively common.

VC55 Status

Uncommon or under-recorded.

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Leicestershire & Rutland Map


Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map