[Microsomacanthus paraparvula sp. n. (Cestoda: Hymenolepididae)--a parasite of diving ducks in Chukotka].

Microsomacanthus paraparvula sp. n. differs from all other species of the genus by extremely small length of proglottids and genital organs. The size and general shape of the hooks closely resemble those of M. parvula (Kowalewski, 1904). However, the new species performs twice as many proglottids for the same specimen size. The dimensions and topography of the internal organs are also different, the cirrus sac size being one third of that in M. parvula. Finally, the new species represents a distinctly different life cycle using the caddisfly as the intermediate host.