In Lord of the Flies, what motivates Jack to do what he does with the sow's head?
A pivotal chapter in Lord of the Flies, Chapter Eight marks the establishment of anarchy as Jack and the hunters descend completely into savagery, killing the sow in a perverse manner, cutting its head off and impaling it on a stick, and stealing the fire, the symbol of power and rescue by civilization.
Clearly, power shifts in this chapter as Jack asserts his power, symbolized by his theft of the fire that is suggestive of Promethesus's having stolen fire from the gods and enabled the mortals with it.
Jack began to clean his bloody hands on the rock.
"How can we make a fire?"
We'll raid them and take fire. we'll put on paint and sneak up; Roger can snatch a branch while I say what I want....
Likewise, Roger's sadistic slaying of the pig and Jack's cutting off of its head and impaling it upon a stick is symbolic of his murder of civilized behavior. Further, Jack cuts off the head of the sow as an offering to "the beast." Jack is now a savage chief, and he offers his sacrifice to the powers of evil, Beelzebub because he embraces this evil that is innate within him.