Arion rufus (Linnaeus, 1758) Chocolate Arion
Arionidae, Stylommatophora, Gastropoda, Mollusca, Animalia
Contracts to hemisphere when not actively crawling, and if disturbed will often rock from side to side; in young specimens (about 25 mm long) the back is dark and the sides are lighter, the darkness extends downward as the slug grows; head and tentacles dark; when mantle bands are present (in young), the right band passes above the breathing hole; mucus sticky; in woods and gardens; omnivorous; serious pest; eggs opaque white becoming yellow brown as they develop, several dozen per cluster, 5 x 4 mm; color ranges from red-brown, through chocolate brown with or without orange on the foot fringe, to black; native in northwestern Europe; in western Washington, the chocolate ecotype is most common in urban areas, while the black ecotype is more common in forested habitats. A similar species in Europe, A. ater, tends to be black and more urban, and is separable from A. rufus only by dissection or molecular analysis. Although A. ater has apparently mistakenly been reported from North America, dissection has not confirmed its presence in the Pacific Northwest or in North America.