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]