a family of tapeworms having a strap-shaped body that measures 3 to 200 cm in length. The Ligula and Digramma are not divided into proglottids, whereas the Schistocephalus are segmented even in the larval stage (plero-cercoid). The anterior end of the body has two longitudinal bothria—sucking depressions. The numerous hermaphroditic sexual systems are arranged in one or, less commonly, two lengthwise rows.
The developmental cycle includes two intermediate hosts: the first is a copepod (Cyclops, Diaptomus), and the second a freshwater fish (cyprinid, groundling, stickleback, goby). The procercoids, which develop in the body cavity of the fish, are dangerous parasites causing epizootic disease and death among the fish population. The larvae become sexually mature tapeworms within 30 to 50 hours after entering the intestine of a fish-eating bird. Their eggs must enter water in order to develop.
The family Ligulidae contains eight species, which are found wherever appropriate fish hosts dwell.