Hippoboscidae, the louse flies or keds, are obligate parasites of mammals and birds. In this family, the winged species can fly at least reasonably well, though others with vestigial or no wings are flightless and highly apomorphic. As usual in their superfamily Hippoboscoidea, most of the larval development takes place within the mother's body, and pupation occurs almost immediately.

Sheep or domestic sheep are a domesticated, ruminant mammal typically kept as livestock. Although the term sheep can apply to other species in the genus Ovis, in everyday usage it almost always refers to domesticated sheep. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Numbering a little over one billion, domestic sheep are also the most numerous species of sheep. An adult female is referred to as a ewe, an intact male as a ram, occasionally a tup, a castrated male as a wether, and a young sheep as a lamb.