Black slug, Arion ater "Black slug" by Alexfiles via Flickr, Creative Commons Attribution ShareAlike.	Arion circumscriptus James K. Lindsey via Wikicommons, Creative Commons Attribution ShareAlike.
Arion fasciatus Magne Flåten via Wikicommons, Creative Commons Attribution ShareAlike.	Arion fuscus Michal Maňas via Wikicommons, Creative Commons Attribution ShareAlike.
Arion distinctus Michal Maňas via Wikicommons, Creative Commons Attribution ShareAlike.	Arion hortensis "Sluggy" by MonkeySimon via Flickr, Creative Commons Attribution.
Spanish slug, Arion vulgaris "Nacktschnecke" by Dr. EOS via Flickr, Creative Commons Attribution-NoDerivs.

Taxonomy:

Arion (Add)

Black slug, Arion ater

Red slug, Arion rufus

Arion (Carinarion) (Add)

Arion circumscriptus

Arion fasciatus

Arion silvaticus (Add)

Arion (Mesarion) (Add)

Arion fuscus

Arion subfuscus (Add)

Arion kobeltia (Add)

Arion alpinus (Add)
Arion anthracius (Add)
Arion distinctus

Arion fagophilus (Add)
Arion hortensis

Arion intermedius (Add)

Arion lusitanicus
Spanish slug, Arion vulgaris

Kootenaia burkei (Add)

Nipponolimax monticola (Add)