Abstract
The life histories of Haustorioides japonicus KAMIHIRA and H. munsterhjelmi (OLDEVIG), amhipods were investigated in the sandy beaches of the southern part of Hokkaido, Japan. There was a delicate difference in the alternation of generations of H. japonicus in each study. A bivoltine reproductive cycle was exhibited in Date-usu : a generation recruited in spring produced in summer a generation that overwintered and reproduced in the following spring. On the other hand, the univoltine reproductive cycle was observed in Hakodate. In Iwanai and Setana, the majority of numbers were univoltine, and a small number were bivoltine. It seems that the main reason for the differences in alternation of generation was the level of the sea water temperature in spring and summer in each study area. H. munsterhjelmi showed a univoltine reproductive cycle in Mukawa-shiomi. The habitat of these amphipods was observed in the littoral zone and the sublittoral zone. The breeding season was spring or summer.
