In Lord of the Flies what does Beast from the Water and Beast from the Air symbolize?

The "Beastie" as well as the sow's head represents evil and savagery in "The Lord of Flies". Only Simon is able to rise above the base cruelty and evil that manages to take over the other castaways. He knows the fear of the "Beastie" stems from the fear of the beast within all of them.