Abstract
Linear relationship was found between the cumulative heat units above the lower threshold of development and the probit of cumulative percentage of adult catches. The cumulative heat units estimated by using the equations were 120 day-degrees for the development from pupa to adult in the overwintered generation and 430, 480, and 580 day-degrees for the completion of development (egg-adult) in the 1st, 2nd, and 3rd generations, respectively. Diapause was induced under the condition of short day-length, and the critical day-length was estimated to be about 13hr. 30min.
