This paper deals with the results of investigations on the faunistic composition and one affected by the applications of insecticides(Meobal 2 per cent and Kuledal 2 per cent dust) in paddy field. These experiments were made on June to September, 1967 in Shimane university farm.
1. The composition of major species in the paddy field is shown in Table 2-8.
2. The succession of the structure of arthropod community in the paddy field is summarized as follows : The population number recognized in the paddy field applied the dusting of Meobal(2 per cent dust at the rate 3 kg. to 10 are) were in order of Chironomus oryzae＞Parasitic wasps＞Hydrellia griseola = association on June 24 and applied field with 2 per cent dust of Kulebal were in order of Chironomus oryzae＞Aphididae＞Hydrellia griseola = association on September 16. The population shown in unsprayed field were Hydrellia griseola＞Chironomus oryzae＞Nephtettix apicalis cincticeps = association on June 24, and Chironomus oryzae＞Aphididae＞Sogata furcifera = association on September 16.
3．The geometrical progression formula log y＋ax = b, given by Motomura(1932) is shown in Table 10 and Figure 2～5. The number of individuals was observed to decrease by the application of insecticides.
4. The most important injurious insects recoginzed in paddy field were Nephtettix apicalis cincticeps, Sogata furcifera, Nilaparvata lygens, Delphacodes striatella, Inazuma dorsalis and Chilo suppressalis.