In The Lord of the Flies the motif of blood serves to symbolize the loss of innocence.
A motif is a repeated symbol used in a story. In this case, the reoccurrence of blood is used to track the boys’ fall from innocence. The assigning of hunters and the face painting are the first signs of savagery.
When blood is first discussed, it is for a practical and intellectual purpose. The boys need to hunt to be able to eat, and they discuss the reasons for letting out a pig’s blood. Jack comments that you need to let the blood out of the pig or you can’t eat the meat. This is certainly one of the most rational things Jack says. However, this practical need for blood soon turns to a symbolic one, as the boys gain a bloodlust.
At first, Jack does not want to actually bleed the pig.
They knew very well why he hadn’t: because of the enormity of the knife descending and cutting into living flesh; because of the unbearable blood. (ch 1)
Somehow, the boys seem to know that once they see blood there will be no turning back. They will turn into something else. As the boys descend into savagery, they lose the remnants of civilizations in their personalities.
He began to dance and his laughter became a bloodthirsty snarling. …and the mask was a thing on its own, behind which Jack hid, liberated from shame and self-consciousness. (ch 4)
The mask of the face paint is directly related to the blood. The mask turns the boys into something else. They are hunters, and they are no longer responsible for their actions. Notice the significance of the boys’ chant.
“Kill the pig. Cut her throat. Spill her blood.” (ch 4)
Jack’s bloodlust becomes a key point of contention between Ralph and Piggy and his hunters.
“You and your blood, Jack Merridew! You and your hunting! We might have gone home—” (ch 4)
When the boys put the pig’s head on a stick as an offering for the beast, Simon becomes obsessed with it. He realizes the destructive power of the blood, and soon the blood does not just destroy him, it destroys them all. It destroys their innocence, and even after they are rescued the survivors will never be the same.