抄録
The Yokohama population of Hyphantria cunea took 8, 38 and 13 days for development of the egg, larval and pupal stages, respectively, at 25°C. A sum of 800-900 degree-days above 10°C was thus required for completing the nondiapause generation. Some pupae raised in a long photoperiod were, however, in a state of arrested development for about a week at 25°C, which resulted in bimodal emergence of adults. The ture winter diapause lasted much longer periods, being induced by a short photoperiod during the larval stage. The critical (median) photoperiod for the induction of the winter diapause at 25°C was between 14 hr 30 min and 14 hr 45 min, although it might be shorter than this at a higher temperature. These data were superimposed on the photothermographs of different parts of Japan in order to predict the seasonal life cycle and the local adaptability of the species. In the Tokyo-Yokohama area, the predicted life cycle conformed well to field observations. It was suggested that this psecies would require some genetic changes for establishing in Hokkaido or in the southern part of Kyusyu. At present, local samples collected from the northern front of distribution (Omagari, Akita) did not show any sign of divergence in the photoperiodic response.
