Diapause is a genetically controlled life phase in which the biochemical and behavioral adjustaments that occur in advance are followed by a refractory period of suppressed development. In this study, we investigated whether spermiogenesis in phytophagous bugs continues in adult diapause. The morphology of spermiogenesis during this phase was also examined. During diapause, the testes of phytophagous insects contained vesicles similar to residual bodies. These vesicles showed acid phosphatase activity, which suggested that they were active lysosomes. In addition, the nucleus of spermatids showed an apoptotic pattern with fragmented chromatin. These results indicate that spermiogenesis is discontinued during adult diapause in these bugs, and that apoptotic and phagocytic events may be involved.