Published online by Cambridge University Press: 10 July 2009
Wind tunnel studies were conducted on the influence of pheromone dose and wind speed on the response behaviour of the larger grain borer, Prostephanus truncatus Horn to its male-produced aggregation pheromone. The pheromone did not increase the proportion flying and non-optimal dosages reduced flight initiation. Beetles flew at progressively lower airspeed and net upwind velocity as the pheromone dose was increased from 0.02 mg to 4 mg. Also, at the higher doses, the latency of take-off was longer. However, at the intermediate dose of 0.2 mg, take-off latency was significantly shorter, and the proportion of beetles exhibiting phototaxis at this dose was at a minimum. Wind was necessary for the beetles' orientation to pheromone, supporting the pheromone-induced anemotaxis hypothesis. Flying beetles increased their airspeed and net upwind velocity and therefore flew faster at the higher wind speeds. These results suggest that pheromone dose and wind speed are major influences on the flight behaviour of P. truncatus, and the implications of this on the interpretation of field pheromone-baited trap catch data are discussed.