These are parasites of birds and mammals.
Adults live in the intestine of birds and mammals. Insects and myriapods are the intermediate host. Paratenic hosts may be used.
Main longitudinal lacunar canals are dorsal and ventral. Giant nuclei are present in cement glands and lemnisci but not in body wall. Cement glands in male are separate. There are two ligament sacs in the female and they persist throughout life.