Chewing and sucking lice are ectoparasites (EHK-teh-PAE-rih-saits), organisms that live on the outside of their host organism. All species spend their entire lives on the body of the host animal. They require the constant temperature and moisture of this habitat to feed and reproduce. Most species of lice are found only on a single kind of host or on small groups of closely related species.
More than 4,300 species of chewing lice have been found on 3,910 different kinds of animals, including 3,508 species of birds and 402 species of mammals. All orders and most families of birds have chewing lice. Five hundred and forty-three species of sucking lice have been found on 812 species of mammals. Mammals that do not have lice include bats, whales, dolphins, dugongs, manatees, pangolins, echidnas, and platypuses.
Although the host body would seem to be a uniform habitat, it is actually a series of smaller habitats that differ slightly in terms of temperature and moisture. For example, the different parts of a bird's body, such as the head, back, wings, and rump, are completely different habitats from the viewpoint of a louse. These different habitats might allow several species of lice with slightly different temperature and humidity requirements to live on the same host animal without having to compete with one another directly for food and space. Some species occupy more than one part of the body at different times in their lives. For example, a species of lice live inside the throat pouches of pelicans and cormorants where they feed on blood.
However, they must return to the head feathers to lay their eggs.
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