Abstract
The effect of the strength of beating on the proportion of mites falling must be considered in order to estimate the total number of mites on the basis of the partial number of mites falling. A twig (10cm long) of sugi, Cryptomeria japonica (D. DON), was dropped onto a white paper from different heights as an index of the strength of beating. The process of the number of mites falling was simulated well by WADA's beating model. The total number of mites, however, was underestimated considerably because the estimated value was equal only to the possible number of mites falling which was related exponentially to the strength of the beating. An improved model that well explained the above relationship was formulated and proved to be applicable for the estimation of the actual number of mites. For this purpose the twig (10cm or 15cm long) has to be grasped loosely by hand and struck strongly against the paper.
