Abstract
The mating behavior of Hyphantria cunea DRURY was obseved in detail in order to analyze the mechanism of the male approach. Virgin females take a calling pose near the lower crown layer of the host trees, when such a layer is more than 2 meters high. When the tree is less than 2 meters tall, they position themselves in the upper layer of the crown. The males fly near the host trees like gas molecules moving in a packed vessel. Examination of the behavior of a male coming into the effective sphere of a sex pheromone revealed four types of male flight : 1) some moths pass straight through the area without turning, 2) some give up repeated turns on the way of zigzagging flight, and 3) the others succeed in reaching a virgin female; 4) the male turn is a windward turn. The male approach to a calling female can be explained if the upwind turn is defined as an encounter between a zigzag-flying male and a flowing flamentous pheromone puff.
