Human head louse, Pediculus humanus capitis, photomicrograph
The head louse (Pediculus humanus capitis) is an obligate ectoparasite of humans. Head lice are wingless insects spending their entire life on human scalp and feeding exclusively on human blood. Humans and chimpanzees are the only known host of this specific parasite, but many other species of lice are known which infest most orders of mammals and also head louse differs from the related body louse in preferring to attach eggs to scalp hair rather than to clothing. Although the two species are visually identical, they do not normally interbreed, although they will interbreed in laboratory conditions. From genetic studies of them, they are thought to have diverged as species about 107,000 years ago, when many humans began to wear a significant amount of clothing. A yet more distantly related species of hair-clinging louse, the pubic or crab louse (Pthirus pubis), also infests humans. It is visually different from the other two species, and is much closer in appearance to the lice which infest other primates. Lice infestation of any part of the body is known as pediculosis. Head lice differ from other hematophagic ectoparasites such as the flea in that lice spend their entire life cycle on a host. Head lice cannot fly, and their short stumpy legs render them incapable of jumping, or even walking efficiently on flat surfaces.
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Photo credit: © Scenics & Science / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: blood, capitis, folicle, hair, head, human, humanus, itch, louse, nits, parasite, pediculus, photomicrograph, scalp, school
