Vertical and horizontal movement by slugs

Abstract: Following treatment with molluscicides, slugs can recolonize a site very quickly, butwhat proportion of the colonizing slugs move from adjacent areas (horizontal movement) and whatproportion from within the soil (vertical movement)? On a grassland site barriers were used to trapand exclude slugs to estimate horizontal and vertical movement over a period of 32 months. For thefirst 15 months vertical movement made a significant contribution to the slugs recolonizing thearea. The ecological mechanisms and the implications for control of slugs are discussed.