Nick Upton / 2020VISION / Black slug (Arion ater), brown form, crawling over patio after rain, with house and garden bench in the background, Wiltshire, UK, July . Property released.

Martin Dohrn / Red forms of Black slug {Arion ater} mating, Northern Italy, Europe

Jason Smalley / Close-up of Slug {Arion ater rufus} feeding on leaf, UK

Chris Mattison / Black Slug (Arion ater) grey form. Yorkshire, UK, September.

David Woodfall / Black slug feeding on grasses in early morning dew, Gilfach Nature Reserve, Radnorshire Wildlife Trust, Powys, Wales, UK

Rod Williams / Black slug (Arion ater) orange form on leaf, South London, UK, September

Rod Williams / Black slug (Arion ater) orange form on leaf, South London, UK, September

Nick Upton / 2020VISION / Black slug (Arion ater), brown form, crawling over patio after rain, with house and garden bench in the background, Wiltshire, UK, July . Property released.

Alex Hyde / European black slugs (Arion ater) brown variety, mating on leaf litter, Midi-Pyrenees, France. August.

Simon Colmer / Portrait of Black slug, (Arion ater) white form, England, UK

Mark Bowler / Common black slug (Arion ater) orange blonde or white form

Mark Bowler / Common black slug (Arion ater) brown form on lettuce

Mark Bowler / Common black slug (Arion ater) white, orange or blonde form

Mark Bowler / Common black slug (Arion ater) brown form

Mark Bowler / Great black slug (Arion ater) brown form, viewed from above

Mark Bowler / Common black slug (Arion ater) brown form on lettuce

Mark Bowler / Great black slug (Arion ater) brown form

Philippe Clement / Black slug {Arion ater} eating Russula toadstool, Belgium

Philippe Clement / Black slug, orange form {Arion ater} La Brenne, France

GEORGETTE DOUWMA / Great black / Large red slug (Arion ater) Various colour forms: orange-red commonest in south and in gardens while black form prevails in north and upland areas. UK

GEORGETTE DOUWMA / Great black / Large red slug (Arion ater) Various colour forms: orange-red commonest in south and in gardens while black form prevails in north and upland areas. UK

Michael Hutchinson / Large Black Slug {Arion ater} hanging from grass by slime after slipping off the tip, Bristol, UK

Michael Hutchinson / Large Black Slug {Arion ater} on grass seed head, Bristol, UK

Michael Hutchinson / Large Black Slug {Arion ater} attached to grass by slime, Bristol, UK

Michael Hutchinson / Large Black Slug {Arion ater} attached to grass by slime, Bristol, UK

Nigel Bean / Black slugs mating {Arion ater} UK

Nigel Bean / Black slugs mating {Arion ater} UK

Kim Taylor / Black slug, orange form {Arion ater} showing spiracle, UK.

Michael Hutchinson / Black slug, red form {Arion ater} England

PREMAPHOTOS / Black slugs mating {Arion ater} red form, England. Hermaphrodite

Adrian Davies / Black slugs (Arion ater) mating. England, UK, Europe

Adrian Davies / Slugs mating {Arion ater} UK