Natural Resources Institute, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK.
Prostephanus truncatus, commonly known as the Larger Grain Borer (LGB) is a destructive pest of stored maize and cassava in the tropics. Traps baited with artificial Larger Grain Borer aggregation pheromone are used to monitor the spread of this pest across Africa. Teretrius nigrescens (Tn) is an Histerid beetle that preys upon LGB e ggs and larvae. LGB male-produced aggregation-pheromone is used as a kairomone by adult Tn, and Tn is also caught in traps baited with LGB aggregation pheromone. Tn has been released in some African countries as a biological control agent against LGB. Extensive trapping data is being used to assess the impact of this biological control programme. In the near future, trap catches may also be used to predict years of particularly high risk for farmer's stored food. Some interesting patterns have emerged in the trap catch data: First, there is a very close short-term temporal correlation between catches of predator and prey (likely to be climatic influences on dispersal or efficiency of the trap). Second, the extent to which traps interfere with each other (i.e. the presence of extra traps depletes the catch per trap) is different between predator and prey. Third, there is an unexplained regular fluctuation in trap catch of prey soon after a trap is first baited with a pheromone capsule. We are hoping to use this opportunity to generate discussion and ideas to explain these phenomena.