Prey selection and foraging behaviour by Pterostichus cupreus L. (Col., Carabidae) under laboratory conditions

Several authors have indicated that carabid beetles offer potential as pred ators of insect pests on arable crops, but this potential is reduced by the ir limited ability to climb the crop plants. In the current investigation a n initial laboratory experiment indicated that seven species of carabid bee tles commonly found in arable fields in the UK would feed on both aphid and collembolan prey. Pterostichus cupreus L. and Bembidion guttula Fabr. were found to accept both live and dead aphids and collembolans. In further lab oratory investigations P. cupreus exhibited greater consumption of the cere al aphid Metopolophium dirhodum Walker than the alternative prey species He teromurus nitidus, Templeton (Collembola, Entomobryidae) and there was some indication of preference for the aphid prey as these were often consumed f irst. Significantly more handling time was required for the consumption of M. dirhodum compared to H. nitidus. The treatments where P. cupreus was giv en a diet of aphids or collembolans prior to the prey choice experiment, di d not appear to influence the number or type of prey items consumed. Using a four-arm olfactometer P. cupreus reacted positively to the volatile s from collembolans, but gave a less clear response to those from the cerea l aphid M. dirhodum. In an artificial field arena P. cupreus readily climbe d barley plants in search of M. dirhodum, perhaps as a response to volatile emissions, but this behaviour changed when H. nitidus were introduced onto the substrate of the arena. Although the current results indicated that P. cupreus has potential for the control of cereal aphids, the presence of al ternative prey appeared to reduce this potential and suggest that the carab id is an opportunistic feeder.