In this chapter, "Beast from Air," what Samneric assume is some sort of beast is actually a fallen paratrooper with his parachute. An explosion occurred during the night, presumably the plane being shot down. Although the airman parachuted out of the plane, he evidently died in the blast. This beast reinforces Golding's theme of the degeneration of society due to moral collapse. Ironically, just as Ralph is fixated on keeping the fire going so the boys can be rescued, we get a glimpse of the outside world as it collapses. It is, after all, a nuclear war that has resulted in the boys' being taken from their homes and ultimately stranded on this island. The outside world is deteriorating quickly, and the boys have a chance to remake society without the follies that their parents' generation has succumbed to. Unfortunately, the boys end up remaking a world full of hatred, schism, murder, and war--just like the world outside.
This "beast from air" is only an outward sign of the true beast, the one Simon meets in chapter 8, the one that is "part of you." The way that the parachute makes "the figure bow forward again, sinking its head between its knees" as it blows the corpse along is a symbolic representation of the despair with which Golding views mankind. As Golding looked over the post-World War II society he lived in and considered the destruction that the evil within man is capable of producing, we can envision him like this beast: "the figure sat on the mountain-top and bowed and sank and bowed again," if not in prayer, then in utter despair.