1956 5438+00 In June, Qingdao held the second national general meeting of the Chinese Zoological Society. Zhu Xian, an experimental biologist, told a story: 1774, the king of Prussia ordered the elimination of sparrows and announced that there was a reward for killing sparrows. People are scrambling to catch birds. Soon, all the sparrows were caught, but the orchards everywhere were full of pests, even without leaves. The king had to take back his life in a hurry and go somewhere else to bring the bird back for protection. Zhu said: "Sparrows are harmful in some seasons, but beneficial in other seasons."