Aploparaksis borealis sp. n. (Cestoda: Hymenolepididae) from passeriform and charadriiform birds in Chukotka and Alaska.

Aploparaksis borealis sp. n. (Cestoda: Hymenolepididae), from the long-tailed jaeger, Stercorarisu longicaudus Vieillot, on the Seward Peninsula, Alaska, and from the red-throated pipit, Anthus cervinus (Pallas), and the Lapland longspur, Calcarius lapponicus (Linnaeus), in Chukotka, northestern Siberia, is described. This cestode is distinguished by the structure of the cirrus and other morphologic characters from other species of Aploparaksis Clerc 1903 in which there are 10 rostellar hooks and the vitelline gland is aporal to the ovary. A. borealis is the first species of Aploparaksis to be reported from birds representing 2 orders (Passeriformes and Charadriiformes).