In the novel Lord of the Flies, the boys' fear on the island manifests itself in the form of a "beastie" or "snake thing." As their time progresses, the boys openly refer to the beast in assembly as the reason for the littluns' continued nightmares as well as why one must not venture into the jungle at night alone. In this way, the beast symbolizes fear itself; the boys speculate as to its origin and where the beast could possibly hide on the island.
Their fear of the beast culminates in the landing and subsequent spotting of the parachutist; Samneric mistake the dead parachutist for a horrible creature on the mountainside. Ultimately, the boys' imagined beast is much more horrible than the actual reality of the dead man with the parachute; they let their unchecked fears get the better of them.