Insect script was a special style of calligraphy current in the Spring and Autumn Period and the Warring States Period, also known as “bird-and-insect script” and “bird-and-insect seal script.” It was a variation of seal script. Characters written in this style resembled birds and insects in nature, hence the name. Insect script was cast or inscribed on weaponry, bells and cauldrons. For example, the 8-character inscription on the sword of Goujian, the king of the State of Yue, unearthed near Yichang in Hubei Province, adopted this very style. There were eight styles of calligraphy in use during the Qin Dynasty, among which insect script was in the fourth place. After he usurped the throne, Wang Mang (45 BCAD 23) ordered that insect script be recognized as one of the six official scripts and be used for writing on flags, tallies or seals.
From then on, the Qin Dynasty boasted eight scripts: (1) greater seal script; (2) lesser seal script; (3) engraved script; (4) insect script; (5) ancient imperial seal script; (6) official script; (7) weaponry script; and (8) clerical script. (Xu Shen: Preface to Explanation of Script and Elucidation of Characters)
Chinese characters may be divided into six forms. They are: archaic style, script adapted from archaic style, seal script, clerical script, deviant seal script, and insect script. One must be well versed in all forms of writing ranging from ancient times up to this day to be able to inscribe seals and write on tallies. (The History of the Han Dynasty)