The earth in the cave was eaten by cicadas. It takes about three years for cicada eggs to form cicadas after they fall into the soil. In such a long time, cicadas grow and develop in the soil without food supplement, and the soil will contain certain nutrients, so cicadas eat the soil in caves.

In the process of growth and development, with the increase of the monkey's volume, the soil in the cave is squeezed to the surrounding cave wall. Because the soil itself is loose and the monkey secretes a kind of mucus, the soil itself has not been reduced, but the monkey has made the soil in the cave solid.

Characteristics of cicada

Cicada has a pair of big compound eyes, located on both sides of the head, with three punctate monocular eyes in the middle. Its tentacles are short and hard. At the same time, cicadas have two pairs of membranous wings, which are basically the same in shape, with a wide and short head and protruding forehead and lip base.

The adult body length is mostly between 2 and 2-5 cm; The mouthparts are slender, and there are esophagus and saliva tubes in the mouthparts, which belong to the piercing-sucking type. It is distributed in temperate and tropical regions and inhabits deserts, grasslands and forests.