The origin of the Book of Birds and Insects is quite early, and it appeared on weapons during the Spring and Autumn Period and the Warring States Period. There are "Insect Calligraphy" in Qin Shu's Eight Styles, which are mainly used to write flags and symbols, and also used as seal script.
At first, the bird insect body only added some bird or insect shapes to the strokes of seal script, and later it developed to replace the strokes of seal script with insect bird shapes. Its fonts are circled and bent with pens, with strokes beginning and ending, and many decorations. Its configuration is mostly simplified to bird shape. Although it is impossible to specify what kind of animal shape it is, it is like a crawling reptile.
"Birds and Insects" was originally produced only for beauty. Later, because of the complex strokes and diverse patterns, it was difficult to copy, and it was also used to write documents and letters. In writing, the book of birds and insects can best reflect the southern cultural characteristics of writing. Of course, it is not unique to Wu Yuechu, and its scope of application covers the southern half of China.