Photoperiodic induction of summer and winter diapause regulated by opposite temperatures

Temperature has generally been known to influence the photoperiodic control of summer diapause as well as winter diapause. In both cases, high temperature acts in unison with long photoperiod, and low temperature with short photoperiod. Therefore, it is generally thought that high temperature favors the induction of summer diapause and low temperature tends to prevent it, whereas high temperature suppresses the induction of winter diapause and low temperature enhances it. However, our experimental results from both laboratory and field studies reveal that high temperatures strongly weakened the diapause-inducing effects of long day-length and significantly reduced the incidence of summer diapause in the cabbage beetle, Colaphellus bowringi and the cabbage butterfly, Pieris melete, whereas winter diapause was induced under autumnal short day lengths in response to high temperatures in the rice stem borer, Chilo suppressalis and the pine caterpillar, Dendrolimus punctatus. We suggest that diapause induction has different evolutionary origins in different insect species, showing the diversity of life-history strategy. The phenomena that low temperature induces summer diapause and high temperature induces winter diapause should be not rare in nature, especially in the subtropical zone.