Simon and all His glory

In chapter 8 of William Golding's Lord of the Flies, there is a short introduction to the actual Lord of the Flies while he talks to Simon. Simon is sitting in his meditation spot, when Jack and his pose come and murder a pig right in-front of him. This causes a mass swarm of flies to come to the carcass' head they left behind as an offering to the Beast. The swarm then is named "Lord of the Flies" but is not given a pronounced shape or form, other than a mass. At first it tries to scare Simon into going back to the other boys and playing peacefully, but sense he doesn't move, it starts to get angry and threatens him. Simon only says one thing- "Pigs head on a stick". This is the picture Simon cannot get out of his head no matter how hard he is trying, and this devil isn't helping obviously. The Lord of the Flies says some things that don't really make sense, one of which being; "This is ridiculous. You know perfectly well you'll only meet me down there-so don't try to escape!"