The mating behavior was observed in numated adults of Riptortus clavatus. The courtship behavior was initiated with either freezing of the male or approach of the female to the male. Then the male quivered, mounted the female, and attempted copulation. The female was usually receptive, although she sometimes rejected the mounting male. Copulation began in a position with male above female, both facing the same direction, and ended in a position with the pair facing opposite directions. The role of olfaction in the mating behavior was examined by removing the terminal antennal segment. The olfactory stimuli from either sex played an essential role in releasing the courthip behavior of the opposite sex. The olfactory stimuli from a male suppressed the rejection of females.