Steve Downer / Close up of a Black slug (Arion ater agg.) feeding on a Plantain lily (Hosta) leaf, Birmingham, England, UK, August.

Steve Downer / Black slug (Arion ater agg.) feeding on a dead Yellow slug (Limax flavus), Birmingham, England, UK, August.

Steve Downer / Black arion slug (Arion ater) moving, viewed from beneath showing ripples or pedal waves used for locomotion.

Nigel Cattlin / Spanish slug (Arion vulgaris) with closed pneumostome on grass, light grey colour variation. Berkshire, England, UK. August.

Nigel Cattlin / Spanish slug (Arion vulgaris) on grass, tan colour variation. Berkshire, England, UK. August.

Cyril Ruoso / Black slug (Arion ater) eating Cuckooflower (Cardamine pratensis), close up. Yonne, Bourgogne-Franche-Comte, France. April.

Nigel Cattlin / Common garden slug (Arion distinctus) with eggs on leaf litter and ground.

Robert Thompson / Spanish slug (Arion vulgaris) in garden, Banbridge, Co. Down, Northern Ireland. August

Robert Thompson / Spanish slug (Arion vulgaris) in garden, Banbridge, Co. Down, Northern Ireland. August

Robin Chittenden / Boy observing Black slug (Arion ater), brown form. Norfolk, UK. September 2017.

Adrian Davies / Slug (Arion sp.) egg cluster. Surrey, England, UK. November.

Adrian Davies / Slug (Arion ater agg) mating pair with sperm mass, Surrey, England, UK. August.