Species can be difficult to distinguish from one another upon cursory examination, because individuals of a species can vary in color and there are few obvious differences between taxa.[3] The color of an individual can be influenced by its diet.[4]
Some Arion are known as
pests, such as A. lusitanicus auct. non Mabille (= A. vulgaris), which damages agricultural crops and
ornamental plants, and A. rufus, a familiar
garden pest.[5]Arion slugs are often transported internationally in shipments of plant products and mushrooms.[6]Arion slugs have been identified in North America and Australia as
invasive species, altering the plants of ecosystems through seed predation and competing with native slugs.[7]
Species
There are approximately 40 species in the genus.[4][8]
^Férussac, A. E. and G. Deshayes. 1819–1851. Histoire naturelle générale et particulière des mollusques terrestres et fluviatiles, tant des espèces que l'on trouve aujourd'hui vivantes, que des dépouilles fossiles de celles qui n'existent plus; classés d'après les caractères essentiels que présentent ces animaux et leurs coquilles. pp. Tome 1: 8 + 184 pp.; Tome 2 (1): 402 pp.; 2 (2): 260 + 22 + 16 pp.; Atlas 1: 70 pl.; Atlas 2: 166 + 5 pl.. Paris. (J.-B. Bailliere).