The morphology of the different larval stages and life cycle of Hypoderaeum
conoideum (Trematoda: Echinostomatidae) are described. The freshwater snai
l species Lymnaea peregra (Gastropoda: Lymnaeidae) serves as the natural fi
rst intermediate host and this and L. corvus serve as experimental first in
termediate hosts. These and other freshwater snails, such as Physella acuta
and Gyraulus chinensis, in turn serve as second intermediate hosts. Adult
worms were obtained from chicks and ducks, but not from rats, mice and gold
en hamsters. The morphology of the larval stages is compared with previous
work on H. conoideum. Several aspects of the biology of the life history st
ages are described with emphasis on the transmission dynamics of the free-l
iving stages. Differential suitability of the snail species that may act as
first and/or second intermediate hosts is studied and discussed.