The great irony in this novel lies in its depiction of childhood. Childhood is often thought of as a time of joy and innocence, and this is the template that the novel consciously works against. It is, in fact, a deliberate ironic reversal of the glowingly optimistic portrayal of boyhood in the nineteenth-century adventure yarn The Coral Island, by R.M.Ballantyne - the book that the rescuing officer alludes to at the end of Golding's novel. In The Coral Island, when the boys are stranded on an island, they prove themselves equal to every challenge, and have some glorious times. In Golding's vastly bleaker tale, the boys, when similarly marooned succumb to primitive instincts, emotions and lusts, despite an initial attempt on their part to forge a well-ordered, properly functioning society of their own. To this end they conceive of an assembly where each boy can speak his mind, as long as he is holding the conch. The conch becomes a symbol of this attempt at democratic organization, and when it is smashed, all-out anarchy is set to ensue.
The beast represents the regressive, primitive side of human nature, which comes to the fore in most of the boys when they find themselves cut off from civilization. It the darkness that is within themselves. The sow’s head, left as a offering to the beast, is a related symbol. It represents evil. Physically, it is the sign of the unrestrained savagery that some of the boys descend to (the sow was killed in the most brutal manner). It also represents evil on a more metaphorical level. It is referred to as the “Lord of the Flies”, which is a title given to Beelzebub, or the devil.