The saying " snakes are lustful " was not common. It usually appeared in novels, comics, games, and other works as a humorous and teasing expression. The origin of this saying is not clear. It may be that some people associate the characteristics of snakes with certain negative behaviors, thus producing this word. From a biological point of view, snakes are a kind of docile animals. They usually don't show excessive sexual desire or behavior. In the novel, using the phrase "snake nature" to describe the nature of a person or thing was a humorous and teasing expression. It should be noted that the use of this word should avoid misunderstanding or discomfort, so it is necessary to pay attention to the context and expression when using it.