About Arion fuscus (O.F.Müller, 1774)
Arion fuscus (O.F.Müller, 1774), commonly called the Dusky Arion, is a roundback slug that reaches 50–70 mm in length. Its body is brown, with color ranging from black-brown, olive-brown, to orange and bright reddish-orange. It has darker lateral bands on its body, and dark pigment extends under the pneumostome from the back to the front. The foot fringe is pale with thin lines, and the sole is uniformly pale or translucent. Tentacles are either pale or dark. When stimulated, it does not contract into a bell shape. This species differs from other Arion species by having yellow-orange body mucus. For its genitalia, the atrium has around half the diameter of the spherical spermatheca, and the oviduct is large and swollen, matching the form seen in Arion lusitanicus. This species is found in countries and islands across Europe and Asia, including Austria, Bulgaria, the Czech Republic (where it is classified as least concern, LC), Germany, Netherlands, Poland, Slovakia, Great Britain, Ireland, China, and other areas. It inhabits spaces under fallen logs and under bark in woodland areas, and can also be found in hedges, gardens, pastures, and dunes.
