Symbolism

The symbolism involved in the third circle could be identified as the fact that the gluttonous spent their lives eating and creating trash, so they became the trash of the 3rd circle.

Cerberus in mythology is known as the "Great Worm", and only allows passage into the underworld if a delicacy is tossed into each of his three mouths, because Cerberus is always hungry. This makes him the fitting guardian of the third circle. Cerberus himself represents glutton.