Predation by the carabid beetles Pterostichus melanarius and Poecilus cupreus on slugs and slug eggs

Predation on slugs, Arion lusitanicus (Mabille) and Deroceras reticulatum (Muller), and their eggs by the carabid beetles Pterostichus melanarius (Illiger) and Poecilus cupreus (L.) was investigated in the laboratory. Slugs of different size and slug eggs were offered to the beetles in petri dishes with and without several alternative prey. Pterostichus melanarius destroyed eggs of D. reticulatum and A. lusitanicus, with a clear preference for D. reticulatum eggs. The availability of some alternative prey types adversely affected feeding on D. reticulatum eggs by R cupreus and feeding on A. lusitanicus eggs by R melanarius. Yet consumption of D. reticulatum eggs by R melanarius was not significantly influenced by any alternative prey. Only P. melanarius killed small D. reticulatum in the presence of alternative prey. This suggests that P. melanarius and R cupreus may have the potential to reduce slug populations in the field by destroying slug eggs and, in the case of P. melanarius, killing freshly hatched slugs.