Shakespeare uses animal motif extensively to convey to the audience Macbeth’s thoughts and also to reflect the progress of the plot in general. In scene i and iii of Act III, horses are mentioned repeatedly. Before delving into these scenes, it is important to note the role of horses previously: recently, Duncan’s fine, well-bred horses turned wild and ate each other.
In scene i, Macbeth urges Banquo to his horse: “Hie you to horse” (III, i, 34) and in scene iii, the murderers that Macbeth hired become conscious of Banquo’s presence: “Hark, I hear horses. ” (III, iii, 8) The horses epitomize the witches’ prophesy that fair will be foul and foul will be fair. Horses that are meant to facilitate transportation (constructive) are now destructive. This change in the influence of horses reflects the deep degree to which disorder and confusion extend in Scotland now.
On a few occasions, Macbeth uses an animal to directly describe his feelings. He does so in scene ii, right after he provokes men into vowing to murder his friend Banquo, by saying his mind is “full of scorpions” (III, ii, 36). Indeed, like venomous scorpions, Macbeth is now fully engaged in harming others. Another example is when Macbeth tells Lady Macbeth that they “have scotched the snake, not killed it” (III, ii, 13), an indication that Macbeth does and will not feel his position is secure until Banquo is killed as well.
It is also worth noting that even though Macbeth is referring to Lady Macbeth’s earlier serpent motif (I, v, 64), Macbeth is comparing the snake to Banquo, while Lady Macbeth compares the snake to Macbeth. This change seems inappropriate, since Banquo does not seem to possess the characteristics that snakes are typically associated with: slyness. Macbeth is in fact deceiving himself into thinking that Banquo is as cunningly treacherous as himself, as is shown in his soliloquy when he thinks: “[Banquo] chid the sisters” (III, i, 56).
During Macbeth and Banquo’s first encounter with the witches, Banquo clearly states that he ”neither [begs] nor [fears their] favours nor [their] hate. ” (I, iii, 60-61) It was Macbeth who criticized the witches of being “imperfect speakers” (I, iii, 70) and demanded to know more. Macbeth is deluding himself into thinking negatively of Banquo to justify himself for murdering his friend, to rid himself of guilt. This effort is in turn a stage of Macbeth’s transformation of losing conscience and becoming one who is full of only greed and ambition.