[2] Only in the 1970s did the amateur malacologist Stella Davies discover that in Britain that name had been applied to three distinct species.

[7] Arion distinctus lacks the prickly tubercles of A. intermedius, and is larger and darker with prominent lateral bands.

[3] The definitive character, distinguishing A. distinctus from all other Kobeltia species, is a conical structure inside the atrium that covers the entrance to the epiphallus,[3][10][11] but it is not developed in juveniles.

[13] In Switzerland it occurs up to 2000 m.[14] It is typically found amongst ground litter or sheltering under wood, stones and soil clods.

Studies in agriculture and horticulture have often not distinguished A. distinctus and A. hortensis, but both species are considered to be economically significant pests.

[15][16] This species is believed native to Western, Northern and Central Europe, but has spread eastwards, particularly in synanthropic habitats.

The development of slugs hatching from eggs laid later in spring appeared to be delayed by the dry summer conditions, generating a bimodal size distribution in autumn, and these slugs only matured in spring, with possibly some delaying further.

Hence, most studies have reported a full range of sizes of this species throughout the year, although reproducing adults are largely absent over summer and autumn.