Arion (Arion) ater (Linnaeus, 1758)
Not aggressive (Rollo & Wellington 1979). Aggregations of A. ater occurs during dry conditions and unfavorable temperatures (Rollo & Wellington 1981).
For defense, A. ater may contract its body and rock from side to side (Kerney & Cameron 1979).
Arion rufus.
External: Largest Arion slug; varies greatly in color from black (northerly or mountain forms) to brown, red, orange or gray (southerly or cultivated land forms); foot fringe tends to be redder than body, with darker transverse lines; gray sole; large skin tubercles; big pneumostome; sticky body mucus may be clear or yellow; can form a hemisphere when contracted (Quick 1960; Kerney & Cameron 1979).
Internal: Ring at base of epiphallus where it enters the atrium; short free oviduct is surrounded by genital retractor; ligula (internal folds) in upper atrium; 18 mm long spermatophore, with serrations along its length and tapered at ends (Quick 1960; Kerney & Cameron 1979).
Atrial ligula is much smaller than in A. rufus (Quick 1960).
Juveniles: Sometimes have lateral bands; 10 mm long and pale yellow or greenish at hatching, gaining pigmentation as they age (Quick 1960; Kerney & Cameron 1979).
Eggs: 5 x 4 mm; opaque; turn pearly white to brown with age; up to 150 eggs per clutch (Quick 1960).
100-150 mm long extended (Quick 1960).
Native to: British Isles, N and central Europe, Iceland, Russia (Quick 1960).
Non-native to: North America (Quick 1960).
Preyed upon by lampyrid beetle larvae (Schwalb 1961, in Stephenson & Knutson 1966).
Grasslands, forests, hedges, gardens, wastelands, bogs; to 1800 m altitude (Quick 1960; Kerney & Cameron 1979). Microhabitat is mostly living plants, with some occupying bare soil or dead plants and logs when available (Cameron 1978). .
Omnivorous. Feed on dead and live plants, dead animals, and feces (Graham 1955; Chatfield 1976).