Pattern of pheromone-oriented flight in male potato tuberworm moths

The pheromone-oriented flight of maleP. operculella was observed under field conditions. Eighty percent or more of the flights were shorter than 1 m. Thus the approach of males of this species to a distant pheromone source is composed of a chain of short flights. The pattern of the flights changed when the males came within about 1 m of the lure, with a decrease of flight speed and an increased tortuosity. This probably facilitates eventual location of the female by a male. Only a few males succeeded in arriving at the high-dose lures. Males did not succeed in arriving at the lure when it was 70 cm above the ground: this was confirmed by a trap test; however, the flight pattern consisted of a chain of short flights even in these cases. The adaptive significance of this flight pattern is discussed.