What animals are the wolf, worm, tiger and leopard? Their meanings and references explained at once

In ancient times, wolf, worm, tiger and leopard referred broadly to all fierce animals, and was also a term used to metaphorically describe wicked people and villains. So what animal does the "worm" in the term generally refer to?

What animal does the worm in wolf, worm, tiger and leopard generally refer to?

Here “worm” cannot mean insects or bugs, nor small animals, nor the tiger, because the tiger is already there and cannot be repeated. So the worm here should refer to the venomous snake (or python). Because the snake is also a very fierce animal, and at the mere mention of it people tremble with fear. In addition, in many places the snake is also called “long worm”, so it also makes sense to say that worm refers to the snake.