[7][9] Countries where it occurs include: Outside Europe it is also known, presumed as an introduction, from: Boettgerilla pallens is very narrow and slender slug, almost worm-like and sharply keeled.

[10] The shell is small, fragile, 1.5–3 x 0.8–1.5 mm, with median nucleus and growth lines, denser in the posterior part, no thin margin, located below the very terminal section of the pointed end of the mantle.

[10] Reproductive system: Penis is elongate and broader than vagina, epiphallus and spermatheca.

[10] Epiphallus is swollen and connected to penis laterally near its posterior end, by a long thin duct, which is thinner than vas deferens.

[10] In Milax gagates the posterior end of the mantle is rounded, its shell is larger and better visible, its colour more yellowish-brownish.

Boettgerilla pallens inhabits a very wide range of habitats, including gardens, grassland, coniferous and deciduous woodland, and is tolerant of a wide range of soil pH, calcium content and water content.

[7][32] It lives at altitudes of up to 1750 m in the Caucasus[3] and in Switzerland at up to 1600 m, but usually below 700 m.[14] It can be considered as synanthropic,[3] although it is now often found also in undisturbed habitats.

[33] Feeding is seldom intensive: slugs usually take a few bites (of earthworm faeces, detritus etc., also arionid eggs) and move on.