To Simon how is the pigs head like devil?

Simon likens the pig's severed head on the stick to the Lord of the Flies, or the devil. Both the pig's head and the devil are seen as symbols of evil and darkness, and both are associated with sacrifice and death. The pig's head is a reminder of the boys' descent into savagery, and of the darkness that lurks within all humans.

Here are some specific details from the novel that support this interpretation:

* The pig's head is described as "grin[ning]" and "white," which are colors associated with death and evil.

* The pig's head is placed on a stick, which is a common symbol of sacrifice.

* The pig's head is surrounded by a circle of rocks, which is a symbol of the boys' cult-like worship of the Lord of the Flies.

Taken together, these details suggest that Simon sees the pig's head as a symbol of the Lord of the Flies, and of the evil that is taking hold of the island.