The pig head, specifically the Lord of the Flies, symbolizes the dark, primal instincts that lurk within human nature.
The boys on the island are initially excited about hunting the pig, viewing it as a source of food and a way to prove their masculinity. However, after the hunt, their actions become increasingly savage, culminating in the ritualistic sacrifice of the pig head. This act represents their descent into barbarity and their embrace of the darker aspects of their nature.
The Lord of the Flies, as a symbol of this primal instinct, speaks to the boys, tempting them with the promise of power and freedom from rules. This temptation leads them to abandon their attempts at civilization and embrace their baser desires.
The flies swarming around the head represent the corruption and decay that are spreading throughout the island and within the boys themselves. This is a stark reminder of the consequences of unchecked savagery.
Ultimately, the pig head serves as a reminder of the potential for evil that exists within all humans. It shows how easily civilization can crumble in the face of primal urges and how essential it is to maintain control over our darker impulses.