Ever since the first intermediate host of Clonorchis sinensis was identified with Bulimus striatulus, it has been place to an important position in epidemics. One way to prevent Clonorchis sinensis is to exterminate Bulimus, which is itself the first intermediate host and there by to separate the life cycle of Clonorchis.

In killing B. striatulus, nicotine sulfate and lindane have been chosen from insecticides which are widely used in farming areas. And then nicotine sulfate and lindane have been used to check their effectiveness in killing B. striatulus. In this experiment, the resistance of cercaria which parasites to B. striatulus has also been studied.

Dipping method was used in the study. Nicotine sulfate and lindane have been used to check the mortality effect. Nicotine sulfate was used to check percentage of mortality in varied times. The existance of cercaria was tried only in nicotine sulfate.

In the experiment of mortality effect of insecticides to B. striatulus and cercaria, the difference in killing rate and the resistance in different concentration and different length of time have been researched.

It resulted as following:

1. In the experiment with nicotine sulfate, the mortality increased with thicker concentration in the constant length of time.

2. When compared the necessary liquid of nicotine sulfate and lindane in LD 50, nicotine sulfate was less used than lindane, but the mortality proved high.

3. In the treatment to the same concentration of nicotine sulfate in different length of time, it proved that the longer period showed higher mortality.

4. The mortality time required in LD 90 of nicotine sulfate was dependent on the concentration. And thicker concentration showed quicker effect.

5. In the resistance of cercaria and B. striatulus to nicotine sulfate, the resistance of cercaria was proved to be stronger than that of B. striatulus.