The incidence of diapause and details of body coloration were examined in adults of the bean bug, Riptortus clavatus (Thunberg) (Heteroptera, Alydidae) under various photoperiodic and temperature conditions. The insects showed a long-day photoperiodic response for the induction of diapause at 20, 25 and 30°C. However, some adults at 30°C failed to enter diapause even under short-day conditions. A photoperiodic response that produced light-colored adults under long-day conditions was common among 20, 25 and 30°C, although high temperature increased the proportion of light-colored adults. The photoperiodic response curve for the induction of diapause and that for in the determination of the coloration of the lateral metathorax exhibited a high degree of similarity at 20, 25 and 30°C, supporting a common time-measurement system for these two responses. With respect to the coloration of the ventral metathorax, temperature rather than photoperiod was the major determinant, although an effect of photoperiod was also detectable. There was no significant correlation between the lateral and ventral coloration in the threshold zone.