Piggy's glasses are crucial to his ability to function within the group, but are stripped from him because they are important to the group as a whole, and in the process he is simply discarded as no longer useful. The pig could be seen as some sort of heathen deity that emerged as an ultimate symbol of power to it's holder, where the conch shell had previously been a symbol to maintain democratic order.
so Piggy's glasses are... innovation and technology? The conch symbloizes rules and structure of society. And I got the pig's head symbolizing the devil. Are these answers okay?
Well, first off... doesn't lord of the "flies" symbol lord of the "rings" ? ...maybe? X)