Abstract. The effect of photoperiod and temperature on the duration of the nymphal period, diapause induction and colour change in adults of Nezara viridula (L.) (Heteroptera: Pentatomidae) from Japan was studied in the laboratory. At 20 °C, the developmental period for nymphs was significantly shorter under LD 10 : 14 h (short day) and LD 16 : 8 h (long day) than under intermediate photoperiods, whereas at 25 °C it was slightly shorter under intermediate than short- and long-day conditions. It is assumed that photoperiod-mediated acceleration of nymphal growth takes place in autumn when day-length is short and it is unlikely that nymphal development is affected by day-length under summer long-day and hot conditions. Nezara viridula has an adult diapause controlled by a long-day photoperiodic response. At 20 °C and 25 °C in both sexes, photoperiodic responses were similar and had thresholds close to 12.5 h, thus suggesting that the response is thermostable within this range of temperatures and day-length plays a leading role in diapause induction. Precopulation and preoviposition periods were significantly longer under near-critical regimes than under long-day ones. Short-day and near-critical photoperiods induced a gradual change of adult colour from green to brown/russet. The rate of colour change was significantly higher under LD 10 : 14 h than under LD 13 : 11 h, suggesting that the colour change is strongly associated with diapause induction. The incidences of diapause or dark colour did not vary among genetically determined colour morphs, indicating that these morphs have a similar tendency to enter diapause and change colour in response to short-day conditions.