The development of the tapeworm Diphyllobothrium latum (L. 1756) (Cestoda; Pseudophyllidea) in its definitive hosts, with special references to the growth patterns of D. dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1827).

When Diphyllobothrium latum develops from larva to adult in a definitive host, it first sheds the entire larval 'body' before growth of an adult strobila starts. This process of shedding off the entire larval abothrial extremity, piece by piece, takes about 48 h. By this time the larva has usually reached the anterior third of the small intestine of the host. D. dendriticum and D. ditremum develop quite differently, although exhibiting similar anterior migrations. In these two species the larvae develop directly into adults without the larval 'body' first being shed. The implications of the observed differences in growth pattern between these three species of Diphyllobothrium to the classification of diphyllobothriid cestodes is discussed briefly.