Predation and scavenging by the generalist predator, Pterostichus melanarius

The research reported in this thesis investigated the ability of P. melanarius to control slug populations, and the impacts that alternative prey, particularly carrion, has on the efficacy of this predator as an agent of slug pest control. A suite of laboratory- and field-based experiments were conducted to achieve those ends. The main findings were: (1) Prey vital status was significant in determining the feeding preference hierarchy of P. melanarius. The mucus defence of live slugs (Deroceras reticulatum) deterred attacks by beetles, but feeding on dead D. reticulatum emphasized a preference for this prey type by P. melanarius. (2) The survival rate of D. reticulatum bitten by P. melanarius was not different to that of non-attacked control slugs. Attacking bites by P. melanarius, visited upon live slugs, did not yield slug DNA-positive results during molecular analysis of beetle foregut contents. (3) Pterostichus melanarius was not able to detect by olfaction the presence of live or 12 h-decayed dead D. reticulatum. (4) The feeding history of P. melanarius had a significant influence on subsequent prey selection. However, the effect interacted with an innate, overarching prey preference hierarchy. (5) A large-scale semi-field experiment identified that P. melanarius fed upon slugs, but the effect of predation pressure was not sufficient to induce negative growth in slug population density. The presence of alternative prey, and the increasing mass of individual slugs exerted rate-limiting effects on slug-predation by P. melanarius.EThOS - Electronic Theses Online ServiceGBUnited Kingdo