When Jack and his hunters set out to kill a pig in the novel 'Lord of the Flies' by William Golding, the superficial reason they have is the need for meat. But their motives (particularly Jack's ( go way deeper than this. Number One, Jack feels ashamed and people who feel shame often feel anger too. What seemed like a pretty good sensible idea (to provide meat as part their diet) at the beginning has now become an obsession, due to Jack's humiliation in failure to make a kill the first time. Now he has something to prove, and will take his fury out on the pig - once he finally gets it. Second, the rational motive to procure meat has been overtaken by an irrational primeval drive for bloodlust and to kill for the sake of it.
In the book "The Lord of the Flies" the boys with Jack as their leader try ad catch and kill a pig but have no luck. Jack continues to track the pig but returns empty handed. Finally, the tribe of hunters, with Jack as their leader, manages to trap and kill a pig. They cut its head off and put it on a stake in the ground. The flies buzz around the head.
Simon while having had a seizure and feeling sick comes upon the head of the pig. He begins to communicate with it. He is delirious and believes that the head is talking to him.