Abstract
Field observations and experimental analyses of the mating behavior of Hyphantria cunea revealed its 4-phased sequence, essential importance of visual cue involved in the sequence, and the fact that the sex-attractant pheromone is effective only in a limited sphere around a female. Mating behavior of the summer generation starts at dawn with the swift and straight-lined "random flight" of males. Males are not guided by the sex-attractant released from females until they come across in contact with its "effective sphere" not exceeding beyond 3 m from a courting female. In this sphere, the male turns to a slow and swinging "searching flight", visually seeking about a whitish object with wings raised. When he finds it, he immediately leaps on it, touches it with his antennae, and, thus recognizing the female contact-chemically mates with her. Detailed analyses of characters of the visual cue is in progress.