The feeding behaviour of Rumina decollata (Subulinidae: Gastropoda) raises questions about its efficacy as a biological control agent for Cornu aspersum (Helicidae: Gastropoda)

The facultative predatory snail Rumina decollata (L.) has been used as a biological control agent for Cornu aspersum (Müller) in Californian citrus orchards for almost half a century despite there being little laboratory and field evidence of its efficacy. We have demonstrated that R. decollata can only successfully kill C. aspersum that are <13?mm (shell diameter) and if given a choice between a known food plant (carrot roots) and C. aspersum within this vulnerable size range, the majority of R. decollata (～93%) chose carrots. Adult R. decollata will feed on C. aspersum eggs and mean total consumption per individual was ～3 eggs over a 7-day period. These experimental results support previous anecdotal suggestions that R. decollata may not be an effective snail predator.