The caudal appendage of a larval cestode, the procercoid stage of pseudophyllid cestodes; it may also be found on the cysticercoid larvae of taenioid cestodes, as well as in many of the hymenolepidids (e.g., Hymenolepis nana). This appendage frequently bears the hooks originally used by the hexacanth in clawing its way into the intermediate host in which the procercoid or other larval stage develops. [G. kerkos, tail + meros, part]