Taxonomy of Human Lice

The following discussion of common and scientific names of human lice is directed at the taxonomically challenged. Hopefully it will reduce the number of erroneous scientific names used to identify these lice. Such errors undermine the public's confidence in opinions rendered by those who study lice, now known as phthirapterists.

Humans are host to lice which are found only on humans. Lice are insects (Arthropoda: Insecta); have three pairs of legs, and body composed of a head, thorax, and abdomen. Most authorities place lice in the insect order Phthiraptera (Arthropoda: Insecta: Phthiraptera). The Phthiraptera include lice which have mandibles and are called Chewing Lice, and lice which have piercing mouth parts and these lice are called Sucking Lice. The Sucking Lice are all in the suborder Anoplura (Arthropoda: Insecta: Phthiraptera: Anoplura). The lice found on humans are Sucking Lice and are placed in two different families. Lice, typically found on the head and on clothing are in the family Pediculidae (Arthropoda: Insecta: Phthiraptera: Anoplura: Pediculidae) and in the genus Pediculus (Arthropoda: Insecta: Phthiraptera: Anoplura: Pediculidae: Pediculus). Lice, typically found on pubic hairs are placed in the family Pthiridae (Arthropoda: Insecta: Phthiraptera: Anoplura: Pthiridae) and in the genus Pthirus (Arthropoda: Insecta: Phthiraptera: Anoplura: Pthiridae: Pthirus). The generic name always begins with a capital, and is italicized, or underlined, to indicate it is from a foreign language (Greek or Latin). The species name of animals always begins in lower case and is similarly italicized. The family name is based on the generic name, however, the suborder, and ordinal names may be independent of the names of lower taxa. See details under Pubic Louse for spelling of the generic and order names.

Body Louse

The scientific name of the Body Louse has had a long and tortured history, which has been discussed in detail by Ferris (1951: 267). The name was fixed in 1958 as Pediculus humanus Linnaeus, 1758. (Hemming, 1958, in "Official List of Generic Names in Zoology," Opinion 104) Thus if the Body Louse is considered a species its binomial name is Pediculus humanus Linnaeus, 1758. If it is considered a subspecies then its trinomial name is Pediculus humanus humanus Linnaeus, 1758. There is no animal known as "Pediculus corporis", "Pediculus humanus corporis" "Pediculus vestimenti" or other synonyms of P. humanus. The question of whether or not the Body Louse is a biological species distinct from the Head Louse is most commonly answered today in the negative. Today the debate centers upon whether or not they merit recognition as subspecies.

Head Louse

It was De Geer in 1767 who first named the Head Louse as Pediculus humanus capitis. Thus those recognizing the Head Louse as a subspecies must use that scientific name. If the Head Louse is considered a species its binomial name is Pediculus capitis De Geer, 1767. No other scientific names are acceptable. Papers presented at the Second International Congress on Phthiraptera provide strong, some may say overwhelming, evidence that there is no morphological, molecular, or behavioral justification for recognizing the Head Louse as being a distinct species or subspecies from the Body Louse. Thus these two common names should be replaced by the common name Human Louse, the scientific name is Pediculus humanus, as used by Kim et al (1986) and others.

Pubic Louse

The Pubic Louse was first described and named in1758, by Linnaeus as Pediculus pubis. In 1815 Leach established the genus Pthirus, and included therein a single species; Pediculus pubis Linnaeus. It is not clear if Leach, or the type-setter, dropped the first "h" in the Greek word Phthirus. Two years later Leach referred to this species as "Phthirus" pubis (Linnaeus). From that time to the present, the generic name has been spelled both ways. However, the generic name was fixed in 1958 as Pthirus (Hemming, 1958, in "Official List of Generic Names in Zoology," Opinion 104). Thus the binomial name for the Pubic Louse is Pthirus pubis (Linnaeus, 1758). No other scientific names are acceptable. "Linnaeus" is placed within parentheses indicating that this was not the original genus in which the author placed this species. This genus, with two species (P. pubis, and P. gorillae) is the only genus in the family Pthiridae, the family name being based upon the generic name. Confusion has been perpetuated by the now common use of the ordinal name Phthiraptera for lice. The names of orders need not be based on the names of lower taxa, thus Haeckel (1896) was free to use the properly spelled Phthirus as the root Phthiraptera for the insect order containing all lice.

References

Ferris, G. F. 1951. The Sucking Lice. Mem. Pac. Coast Entomol. Soc. 1:1-320. 124 figs.

Hemming, F. 1958. Official List of Generic Names in Zoology. First Installment: Names 1-1274. International Commission on Zoological Nomenclature, London.

Kim, K. C., H. D. Pratt, and C. J. Stojanovich 1986. The Sucking Lice of North America. An illustrated manual for identification. University Park: Pennsylvania State University Press, ix + 241 pp.