Why are there so many caterpillars when it rains in Tomb-Sweeping Day?

Twenty-four solar terms are the climatic laws summed up by astronomers and people in ancient China in their life and production practice, which appropriately reflect the changes of temperature, phenology and rainfall throughout the year, and have indispensable guiding significance for people to arrange farming and sericulture activities on time. By Qingming, the temperature is getting warmer and the rainfall is increasing, which is a good season for spring ploughing and spring planting. Therefore, Qingming is an important solar term in ancient agricultural production. The farmer's proverb says, "Before and after Qingming Festival, point melons to plant beans" and "Planting trees is nothing more than Qingming Festival", which is precisely the truth. In the Eastern Han Dynasty, Cui Mang's Moon Order for Four recorded: "Tomb-Sweeping Day ordered a silkworm concubine to stay in the silkworm room ..." It is said that it was at this time that he began to prepare for sericulture. "Tomb-Sweeping Day" is just a solar term, not a festival.

Tomb-Sweeping Day Qi provides important conditions for the formation of Tomb-Sweeping Day customs in terms of time and weather, and this solar term is considered as one of the origins of Tomb-Sweeping Day.