Scolex in the context of "Eucestoda"

Cyclophyllidea (the cyclophyllid cestodes) is the order of Cestoda (tapeworm). It is the largest and most diverse order of Cestoda (tapeworm), encompassing species that infect all classes of terrestrial tetrapods including humans and domesticated animals, and includes species with some of the most severe health impact on wildlife, livestock, and humans.

All have multiple proglottid "segments", and all have four suckers on their scolices (heads), though some may have other structures, as well. Proglottids of this order have genital openings on one side (except in the Dilepididae, which have genital openings on both sides), and a compact yolk gland or vitellarium posterior to the ovary.

Eucestoda, also known as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass being Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodaria. All tapeworms are endoparasites of vertebrates, living in the digestive tract or related ducts. Examples are the pork tapeworm (Taenia solium) with a human definitive host, and pigs as the secondary host, and Moniezia expansa, the definitive hosts of which are ruminants.