Abstract
In order to clarify the existence of the behavioural diapause of Ixodes ovatus adults, the host-seeking and -feeding activities of unfed females that were exposed to a long-day photoperiod (16L-8D) during the egg to unfed adult stages were observed under experimental conditions. The host-seeking activity of the unfed females was rarely observed for about 10 months after molting occurred. The percentage of host attachment for the unfed females was very high (63.3-66.7%) even 1-3 months after they had molted. However, their engorgement percentage was very low (4.4%) even 6 or more months after they had molted. These results suggest that unfed I. ovatus females exposed to a long-day photoperiod enter behavioural diapause and postpone host-feeding and -seeking activities during a period of about 10 months after molting occurred. This diapause seems to explain the disappearance of I. ovatus adults in autumn (October to December) in the Chichibu Mountains.
