Cysticercus is known as the larval form of tapeworm. The structure of cysticercus comprises of a sac filled with fluid. Since tapeworm is a parasite, its larva is found within the tissue of the host.
The larva of tapeworm is also harmful as a full grown adult as it causes cysticercosis in humans which causes mild abdominal symptoms and infection that causes passage of proglottids in the stool
Birds and butterflies don't have a common ancestor because one is a member of a insect and the other is well a bird. They both have different body structure. One has bones and the other has an exoskeleton. hope this helps
