The procercoid is the second[1] larval stage of some tapeworms, which typically develops inside of copepods[2] following their ingestion of the coracidium parasite structure that contains the larval oncosphere.[1] The flatworm in this stage is not enclosed in a protective cyst, but is infectious to the next intermediate host.[3] Procercoids resemble their adult forms in pathways of energy metabolism. They are basically anaerobic, lacking a complete Krebs cycle, and rely on glycolysis.[3]