Multiple mating by females occurs in many insects. However, multiple mating by females increases both the risk and intensity of sperm competition for males. Thus, the male’s ability inhibiting mating receptivity of females represents a highly adaptive strategy to reduce the risk of sperm competition. Males of the seed bug Togo hemipterus (Heteroptera: Lygaeidae) use accessory gland substances to inhibit remating of females. Previous studies showed that a larger body size of male in T. hemipterus had advantageous in pre-copulatory sexual selection (i.e., male-male competition and female choice), but, these did not show the male’s body size effect to post-copulatory sexual selection. Often, in some insects, smaller males take advantageous to post-copulatory sexual selection, for example, by ejaculating a much amount of sperm. However, there is no research focusing on the relation between male body size and the effect of ejaculation, such as inhabitance of female remating. We’ll show the relation between male body size and the effect of ejaculation (inhabitance of female remating) and discuss referring sexual selection and sexual conflict.