How did the characters of birds and insects come from?

The so-called "birds and insects" book is made by further adding decorative changes to the winding of decorative pens and line ends. In fact, many characters in Wang Ziwu Ding have combined decoration with objects and images. For example, the human figure beside the word "Zou" and the ornaments similar to the shape of a human hand and the bird-shaped ornaments with the word "Yong" appear many times. Some scholars have made a detailed study of this kind of calligraphy from the differences of decorative patterns and images, and analyzed it into birds, phoenixes, dragons and insects. We think that from the point of view of calligraphy, such a difference may be of little significance, so we still call it "Bird and Insect Book".