Abstract
A sexually mature female of the brown planthopper, N. lugens, vibrated her abdomen before the male approached her. This abdominal vibration seemed to be induced by the visual cue from the male. The visual cue was also probably important for the male to recognized the female. In some cases, however, the male failed to distinguish females from males of the same species or females of the small brown planthopper, Laodelphax striatellus FALLEN. When a male approached a copulated mature female, she showed a characteristic refusal response; an immature female did not show the response, but escaped the male's temptation. Males preferred brachypterous to macropterous females as their mates when both forms were under their choice. This may be ascribed to a behavioral difference between the two wing forms; the brachypterous female has a stronger tendency to stay on the plant than the macropterous female. The pre-mating period of females ranged from two to five days in the brachypterous form and from three to seven days in the macropterous. Many males became sexually mature within the first day after emergence and most by the second day. There was no apparent difference between the males of the different wing-forms in the frequency of copulation during the adult life. The male's ability to copulate increased for the first five days after emergence and then decreased.
