Studies on Insecticide Resistance of Medical Insects Part II: Study on the development of resistance to insecticide in Korean houseflies (Musca domestica vicina Macquardt)

With regard to the resistance of the Korean housefly, Wheeler et al first observed the susceptibility of the Korean house-fly collected in Seoul to DDT, lindane. dieldrin and malathion in 1956, and found that the Seoul strain was susceptible as compared with various strains in Japan. In 1960, Paik reported that the Seoul strains has a high degree of resistance that corresponds to the fly colony resistant No. 2 at the Orlando Laboratory, Fla.. U.S.A. My observation on the insecticide susceptibility of the strains collected from five localities in 1962, indicated that the Korean strain has a high degree of tolerance to DDT as compared with the strains tested in Europe. He also pointed out that the high degree of tolerance to DDT might be due to some physiological characteristics of the Korean strain. Up to now many experiments on the induction of resistance in laboratory was performed for Musca domestica L. in many countries. However, the results obtained from M. domestica vicina Macquardt are seen quite scarce. Therefore, the writer carried out a study on the development of insecticide-resistance of the Seoul strain of M. domestica vicina under the artificial selection pressures with p,p'-DDT, T-BHC and malathion. Some of the important results so far obtained can be summarized as follows: 1. At the 16 th generation of continuous selection with p,p-DDT, the Seoul strain had become more than 2.6 times as resistant as the original strain. In other word, the LDso was increased only from 69.69 microgram to 188.70 microgram. 2. At the 16 th generation of continuous selection with T BHC the strain had become more than 21.6 times as resistant as the original strain. The LDso was changed from 0.95 microgram to 20.48 microgram. 3. At the 16 th generation of continuous selection with malathion, the strain had become more than 7.8 times as resistant as the original strain. The LDso was increased from 0.68 microgram to 5.29 microgram. 4. In comparison with the results obtained from M. domestica, the increasing of resistance-ratio of M. domestica vicina for DDT was not remarkable. 5. It was observed that the DDT-resistance could not be easily developed by means of conseutive application in the strain which showed the tendency of vigor tolerance like as the Seoul strain