What are the four evils in China's legend?

The legendary "four pests" are mice, flies, mosquitoes and cockroaches.

In fact, the first time to eliminate the four pests was in February 1958, when the Central Committee of the Communist Party of China and the State Council issued the Hygienic Instructions for Eliminating the Four Pests. It is proposed that the task of eliminating flies, mosquitoes, rats and sparrows should be completed within 10 year. Gradually, "sparrow" was rehabilitated and replaced by "bug". Later, due to changes in social life, "bugs" were replaced by "cockroaches". So now the "four pests" should be flies, mosquitoes, rats, cockroaches.

Why do you want to put forward the idea of eliminating four pests? Look at the following introduction and you will understand.

1, mouse: The mouse is a kind of rodent, with different shapes. There are more than 450 kinds. Large number, fast reproduction, strong vitality, eat almost anything, can survive anywhere. It can dig holes, climb trees, climb mountains and wade, waste food and spread diseases, which is extremely harmful to human beings, so it has been hit by human beings, but it is an animal family that can not be killed, so the word "mouse" has a mortar on its head, which means "it can withstand heavy blows". The reason why the mouse is honored as "old" is that it eats, drinks and plays all day, without working, just like a retired person. Rats are easy to adapt to human living environment, so they become the main pests. Rats often haunt sewers, toilets, kitchens, etc. And move back and forth between the bacteria-carrying place and the clean place, and spread pathogens through the feet, body hair and stomach of rats.

2. Flies: Flies have the physiological characteristics of laying eggs for life once they mate. A female fly can lay eggs 5-6 times in her life, and the amount of eggs laid each time is about 100- 150, up to about 300 at most. It can breed 10- 12 generations within one year. Flies are daytime active insects with obvious phototaxis. At night, it stays still. The activity and habitat depend on the species, season, temperature and region of flies. In some seasons, stable rot flies, summer flies and city flies also invade houses. Chrysomya megacephala, Lucilia sericata, Calliphora, Bactrocera dorsalis, Hemp Fly, etc. Mainly active outdoors.

3. Mosquitoes: There is a substance in the saliva of mosquitoes, which has the functions of dilating blood vessels and anticoagulation, making it easier for blood to gather at the bitten place. The substance in mosquito saliva makes the bitten person's skin blister and itch. The prevalence of many infectious diseases is related to mosquitoes.

4. Cockroach: Cockroach is one of the oldest insects on the earth and once lived in the same era as dinosaurs. According to fossil evidence, primitive cockroaches appeared on the earth about 400 million years ago in Silurian. The cockroach fossils we found or cockroaches found in coal and amber are not much different from cockroaches in various cabinets. For hundreds of millions of years, its appearance has not changed much, but its vitality and adaptability have become more and more tenacious, and it has been widely distributed in every corner of the world until today. It is worth mentioning that a decapitated cockroach can live for 9 days, and the cause of death after 9 days is excessive hunger. Cockroaches vomit and excrete feces when eating, and are also the vectors of many infectious diseases.