Tapeworm cysticercus. Scanning electron micrograph (SEM) of the bladder worm or cysticercus stage of the pork tapeworm (Taenia solium), an intestinal parasite. The cysticercus' head, or scolex, is at top. The scolex has the suckers and hooks that will later attach the young pork tapeworm to the gut wall of a human. In its life cycle the pork tapeworm parasite infects humans (its primary host) first and the pig (its secondary host) second. When pork tapeworm eggs from humans enter the pig they form cysts in the muscles, which results in infected pork. If humans eat this, the cysticerci develop into tapeworms in the human intestines. Magnification: x20 when printed at 10 centimetres high.