Taenia

Adults live in the intestine of carnivorous mammals. Gravid proglottids detach and pass in the feces. They are motile and may disperse a short distance from the fecal mass. The eggs can resist environmental conditions for weeks or months until they are eaten by an herbivorous mammal. In the gut of the intermediate host the egg hatches and an oncosphere is released. The oncosphere uses a set of hooks to penetrate the gut wall and enter the bloodstream. The bloodstream transports the oncosphere to the muscles where it develops into a cysticercus larva. Other sites, such as the nervous system, may become infected as well. When the cysticercus is eaten by a carnivore, the scolex of the young cestode everts, attaches to the intestinal lining, and begins growing into a new adult.