Question

why is the speaker called cunning?

Answer 1

The speaker  is  called cunning because he flatters the fly and he wants to dine upon her. He shows false affection towards her.

Answer 2

The cunning word is used for the speaker because he tries to flatter the fly.

On top of that, the reasons for him doing so that he could dine on him.

Hence He started to act fake and make her feel that he is affectionate towards her.

Hence, it shows his cunning nature.