PEDICULUS VESTIMENTI 545 



GENUS PEDICULUS, L. 



All the legs strong. Thumb-like process of the tibia very long and thin, 

 beset with strong bristles. Forelegs somewhat compressed and stronger 

 than the hind. Abdomen elongated, rather narrow, the segments not 

 compressed together ; without lateral tooth-like processes. 



Three species have been included in this genus, viz., capitis, de Geer, 

 corporis, de Geer (vestimenti, Nitzsch) and consobrinus, Piaget. The 

 first two are the head and body lice of man; the third was described 

 from a monkey, Ateles pentadactyliis, and is, according to Neumann, not 

 distinguishable from capitis. The lice infecting man are almost the only 

 ones about which much is known except as regards the external struc- 

 ture ; their life history and bionomics will be discussed later. 



The type of P. capitis* is the louse found on the head of the European. 

 When living on such a host the species is of a whitish or greyish colour. 

 Lice from the darker races of mankind, however, are of a much darker 

 tint, the colouration affecting especially the chitinous plates on the lateral 

 borders of the abdomen and the ventral surface of the sternum, with the 

 result that such specimens show much more definite markings than the 

 type. In addition to the variations in colour, lice from the several races 

 of man show other variations, such as in the proportionate length of the 

 legs and claws, and the presence or absence of serrations on the latter, 

 by which, according to Andrew Murray, who devoted much study to the 

 question in connection with the origin of the races of mankind, the 

 species may be divided into races corresponding to the races of the human 

 species. Later workers, notably Piaget and Neumann, are inclined to 

 lay less stress on these minor differences ; although they undoubtedly 

 occur, they are inconstant, and the distinctions between the races break 

 down when a large number of specimens is examined. 



P. vestimenti (Plate LXIX, fig. 5) is the human body louse, and has 

 received its name from the situation in which it is found. The question 

 possibly an important one for the parasitologist as to whether it is a 

 distinct species, or only at most a subspecies, has been discussed by 

 Neumann, who considers that it should be regarded as a subspecies under 

 the name of P. capitis vestimenti. The differences between the two are 

 certainly very slight, and it is a very difficult matter to distinguish them 

 except from the locality in which they are found. The body louse is said 

 to be as a rule larger than that from the head, and to have more hairs on the 

 integument, its thorax is broader in proportion to its length, and the 



* The louse from which figure 5, Plate L,XVI, was made was taken from a Madrassi, 



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