Geographic variation of the pine moth, Dendrolimus spectabilis Butler (Lepidoptera: Lasiocampidae)

The pine moth, D. spectabilis, has usually an univoltine life cycle in the northern part of Japan, but in the southern part of Japan it has a complex life cycle; the adults emerge once or twice a year alternatively. Overwintering larvae of the pine moth were collected from six localities between 32°49′N and 30°42′N in Japan, to compare the geographic variation of their overwintering stages and their subsequent development. The larvae in the southern localities overwintered at older stages than those in the northern localities. The head widths of the formers were larger and varied wider than those of the latters. After hibernation the formers moulted one to four times before pupation, while the latters moulted four times. The median time of adult emergence after hibernation was shorter in the northern population and the adults emerged within one month. However, some adults of the southern population began to emerge earlier and continue for a long period of months. The larval development, when they were reared under 25°C and 16-hr L, was faster, but the size of larvae as well as the weight of pupae were smaller in the northern population than in the southern.