Pediculus humanus humanus

Pediculus humanus humanus

Human lice can be found anywhere on the planet that is populated by humans. They are more prevalent in areas where people change or wash their clothing infrequently and/or are unclean themselves (Milne and Milne 1980).

  • Biogeographic Regions
  • nearctic
    • native
    • native
    • native
    • native
    • native
    • native
    • native
    • Other Geographic Terms
    • cosmopolitan


    The habitat of the human louse is solely on the human body or in the clothes. They are rarely found elsewhere because they can only survive away from the host for a few days.

    (Milne and Milne 1980)

    Physical Description

    Pediculus humanus is a small insect with a large abdomen and legs equipped with sharp claws for holding onto hair and clothing fibers. The head of the louse ia slightly narrower than the body. They do not have wings like most insects, but they have piercing mouthparts for digging into the skin and draining out the blood. The head louse, Pediculus humanus capitis, is normally 1-2 mm long, while the body louse, Pediculus humanus humanus, also known as the «cootie» is usually slightly larger, 2-3.5 mm. The «nits,» or eggs, of the louse are about 1 mm long and about half as wide. The young lice are often called «red backs,» due to the red color they are because of the blood in them. They turn a grey color once digestion takes place, and is where they get the name «gray back». (Grzimek, 1972; Leftwich, 1977; Milne and Milne, 1980; Roberts and Janovy Jr., 2000)

    • Other Physical Features
    • ectothermic
    • heterothermic
    • bilateral symmetry


    The female lice lay their eggs, which are called nits, singly on the hairs of the host (if they are head lice) or attached to clothing in the case of body lice. The nits will hatch into nymphs in about eight days. The nymphs also suck blood and mature in eight to sixteen days. Each adult female body louse produces between two and three hundred nits in her lifetime, and a single female head louse produces between eighty and one-hundred. Due to this fact and that the generations follow at about three week intervals, a single female could inundate a host in a matter of months (Burton 1968, Grzimek 1972).


    There are very few morphological differences between the two sub-species. The main thing that keeps them separated is their behavior. Body lice live and hide in the folds of the clothing of the hosts, usually close to the skin. They will normally only crawl on the skin in order to feed. Head lice live on the scalp, either attached to the scalp while feeding or to the hairs.

    The lice are transmitted from one person to another by direct contact, by clothes or a brush, or by fallen hair. Anything that has a nit or a female on it will transmit the infestation.

    In the case of head lice, the females are actually specific about the part of the head where they lay their eggs. They prefer to lay them behind the ears or on the back of the head, near the neck line. (Grzimek, 1972; Milne and Milne, 1980; Roberts and Janovy Jr., 2000)

    • Key Behaviors
    • parasite
    • sedentary
    • solitary

    Food Habits

    Lice are obligate ectoparasites. They live off of the blood of humans. They have specially designed mouth parts for piercing the skin of humans and retrieving the blood that is present. (Chew, et al., 08/12/2000; Leftwich, 1977)

    • Primary Diet
    • carnivore
      • sanguivore
      • Animal Foods
      • blood

      Economic Importance for Humans: Positive

      The only way that this species could have any positive economic benefit would be to the people that are involved with selling the drugs and tools used to get rid of an infestation. Today, Lindane, permethrin, and malathion are used to kill the lice. Fine toothed combs are also used in a technique called wet combing, but this is usually accompanied with the use of one of the previously mentioned chemicals.

      (Chew et. al. 2000)

      Economic Importance for Humans: Negative

      P. humanus has relatively little direct effect on its hosts. Bites itch, but do not generally cause other harm. However, lice can be vectors for important diseases. The three most important diseases they can carry are typhus, trench fever (both caused by bacteria in the genus Rickettsia), and relapsing fever (caused by another bacteria species Borrelia recurrentis). These bacterial diseases can now be treated successfully with antibiotics, but in the past, they caused the death of millions of people. Major epidemics strongly affected the political and economic history of Europe and Asia, and liice were the main agents in the spread of these diseases.

      Lice cannot withstand high temperatures, so washing can eradicate the lice. Not until the practice of washing and changing our clothes on a regular basis have we been able to slow the spread of lice, and the diseases that they carry. In contrast to this, their occurrence increases greatly in time of war and hardship because people are closely packed and hygiene is not of high importance.

      (Grzimek 1972; Roberts and Janovy 2000; Milne and Milne 1980)

      Conservation Status

      • IUCN Red List No special status
      • US Federal List No special status
      • CITES No special status


      Chris Morgan (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.


      Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

      living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

      living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

      living in the southern part of the New World. In other words, Central and South America.

      living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

      having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

      an animal that mainly eats meat

      having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

      animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

      having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

      the area in which the animal is naturally found, the region in which it is endemic.

      islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

      found in the oriental region of the world. In other words, India and southeast Asia.

      an organism that obtains nutrients from other organisms in a harmful way that doesn’t cause immediate death

      an animal that mainly eats blood

      remains in the same area


      Burton, J. 1968. The Oxford Book of Insects . Great Britain: University Press.

      Chew, A., S. Bashir, H. Maibach. 08/12/2000. Treatment of head lice. Lancet , 9229: 523-524.

      Grzimek, B. 1972. Animal Life Encyclopedia . New York: Van Nostrand Reinhold Company.

      Leftwich, A. 1977. A Dictionary of Entomology . New York: Crane Russak and Company, Inc..

      Milne, L., M. Milne. 1980. The Audubon Society Field Guide to North American Insects and Spiders . 1980: Alfred A. Knopf.

      Roberts, L., J. Janovy Jr.. 2000. Gerald D. Schmidt and Larry S. Roberts’ Foundations of Parasitology, 6th Edition . Burr Ridge, Illinois, USA: McGraw Hill.

      Human lice, Pediculus humanus, are obligate blood-sucking parasites. Phylogenetically, they belong to several mitochondrial clades exhibiting some geographic differences. Currently, the body louse is the only recognized disease vector, with the head louse being proposed as an additional vector. In this article, we study the genetic diversity of head and body lice collected from Bobigny, a town located close to Paris (France), and look for louse-borne pathogens. By amplifying and sequencing the cytb gene, we confirmed the presence of clades A and B in France. Besides, by amplifying and sequencing both cytb and cox1 gene, we reported, for the first time, the presence of clade E, which has thus far only been found in lice from West Africa. DNA from Bartonella quintana was detected in 16.7% of body lice from homeless individuals, but in none of the head lice collected from 47 families. Acinetobacter DNA was detected in 11.5% of head lice belonging to all three clades and 29.1% of body lice. Six species of Acinetobacter were identified, including two potential new ones. Acinetobacter baumannii was the most prevalent, followed by Candidatus Acinetobacter Bobigny-1, Acinetobacter calcoaceticus, Acinetobacter nosocomialis, Acinetobacter junii, and Candidatus Acinetobacter Bobigny-2. Body lice were found to be infected only with A. baumannii. These findings show for the first time, the presence of clade E head lice in France. This study is also the first to report the presence of DNAs of several species of Acinetobacter in human head lice in France.

      Keywords: Acinetobacter spp.; Bartonella quintana,; France; Pediculus humanus; clade E.

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      • Kingdom Animalia animals

      To cite this page: Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2021. The Animal Diversity Web (online). Accessed at

      Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn’t cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

        | U-M Museum of Zoology
      • © 2020 Regents of the University of Michigan / Comment

      This material is based upon work supported by the National Science Foundation Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.

      Rickettsia prowazekii (Epidemic or Louse-Borne Typhus)


      Control of body lice is the mainstay in the prevention of epidemic typhus. When an outbreak of lice appears, the first step is to change all garments and wash them in hot water. Introducing regular washing of clothes will stop outbreaks. Only when this is impossible is delousing with insecticides useful, such as Lindane in powder form. Application of 30 to 50 g of 1% permethrin dusting powder per adult both inside and outside of clothing and on bedding may be repeated every 6 weeks to kill lice.

      No vaccine is currently available for the prevention of typhus. However, the identification of the attenuating point mutation of a previously successful live vaccine (E strain) that was prone to reversion offers the opportunity to develop a permanently attenuated protective vaccine against R. prowazekii. 62, 63

      Disease Transmission

      The body louse is the vector of three human diseases—epidemic or louse-borne typhus, caused by Rickettsia prowazeki de Rocha-Lima; trench fever, caused by Rochalimaea quintana (Schmincke) Krieg (long known as Rickettsia quintana); and louse-borne relapsing fever, caused by Borrellia recurrentis (Lebert) Bergy et al. (PAHO 1973). These diseases are not presently being reported from the United States, but their introduction at some future time is not impossible if body louse infestations should become sufficiently prevalent. Although head lice have been experimentally infected with Rickettsia prowazeki, neither head lice nor pubic lice have been implicated directly in active disease transmission (Roy and Brown 1954). Although body lice may pose the most serious health threat in many countries, head lice appear to be the greatest nuisance, particularly among school children in highly developed countries where their presence is considered intolerable.

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