The effect of photoperiod on the termination of the behavioral diapause of Ixodes nipponensis adults (Acari : Ixodidae)

Abstract

The effect of the photoperiod on the termination of the behavioral diapause of Ixodes nipponensis Kitaoka et Saito adults reared in a long-day photoperiod (16L-8D) from egg to adult ecdysis was examined in plastic cylinders which were placed outdoors. The vertical activity in a plastic cylinder of I. nipponensis adults which were kept in a long-day photoperiod (long-day group) after they had molted (July 2000) was not found from November 2000 to mid-March 2001. However, the activity of I. nipponensis adults kept in a medium-day photoperiod (12L-12D) for about two months after molting (medium-day group) commenced in November 2000. These results suggest that the behavioral diapause of I. nipponensis adults is terminated by exposure to a medium-day photoperiod. Thus, the medium days of autumn appear to be important to the termination of the behavioral diapause of I. nipponensis adults.