Abstract
1) Objective investigation on the density of fly population was very difficult, because the flies showed excellent fecundity and extensive dispersion. The method taken in the present papar was the one for evaluating the effectiveness of insecticides in field and was to compare with the effectivenss of insecticides before and after application. Evaluation of insecticides in field was desirable for simple and stable method to decrease error caused by apparatus and investigators. 2) Up to the present, the effectiveness of insecticides for flies in field was evaluated by fly trap, fly ribbon and fly grill. However, these had merits and dermits. Of couse, the method with combination of several ones was desirable from the point of ideal view. But, the method by fly ribbon and fly grill were concluded to be useful from the point of practical view. 3) In case of extensive appication of insecticides in field, it was better to evaluate with the method avaraging numerical values. When evaluation of the effectiveness was compared with others in limited area, it was better to pick out numerical value that might represent fly population and that should be a value above the average. 4) In the case of a release study of the dispersion of house fly, the number of flies on fly ribbon indicated the proportional relation with the number of emergence.
