One whose primary source of nutrition is the scenery whlie acting. While some actors may be accused of chewing the scenery in a particular scene, a sceneivorous actor has now evolved into a creature with no other sustenance for his career.

Reference "herbivorous/carnivorous" - plant-eating and meat-eating - as well as "chewing the scenery" as a pre-defined and common critical term for way overdoing it in a performance.

When you eat dirt for the first time and leave your family to build a shack in the woods