Art. 19 LICE OF THE GENUS PEDICULUS EWING 23 



1912 Pediculus capitis Fahrenholz, Jahresb. d. Niedersach. Zool. Ver., 



p. 2, fiss. 1, 3, 7, pi. 3, figs. 3-4. 

 lOlG Pediculus capitis Feuris, Proc. Cal. Acad. Sci., ser. 4, vol. 6, p. 136. 



1919 Pedicxilus humanus, race capitis Nuttall (part), Parasitology, vol. 



11, p. 334. 



1920 Pediculus humanus, race capitis Nuttall (part), Parasitology, vol. 



20, p. 152. 



Female. — Head with well-developed, poorly chitinized neck re- 

 frion; forehead about as broad as long; postocular tubercles well 

 chitinized and w^ith stiff spinelike setae. Antennae considerably 

 shorter than the head; first segment about twice as broad as long; 

 second segment about one and a half times as long as broad; third 

 segment slightly longer than broad; fourth segment of equal length 

 and breadth ; fifth segment about one and a half times as long as 

 broad. Macrochaetae of thorax not equal, the second pair being 

 longer than the others; macrochaeta I about one-half as long as 

 the width of coxa I ; macrochaeta III situated less than the diameter 

 of the thoracic spiracle (bulb of spiracle) behind the same. Pos- 

 terior marginal setae of thorax about fourteen in number on each 

 side; not far from the median line are two pairs of these setae, 

 one pair above the other, which are larger than the others. Tho- 

 racic spiracles the largest of any variety of P. humanus^ being 

 0.134 mm. in diameter (across the bulb). Abdomen long and 

 rather slender; setae, almost without exception, spinelike or peg- 

 like and most of them are not arranged in transverse rows; ventral 

 side of sixth abdominal segment with 11 or 12 setae in transverse 

 row, ventro-lateral pair but little if any larger than the setae in 

 row, discal setae, about 24 in number, are almost as large as those 

 in the row. Pleural plates (fig. 1, A) usually well pigmented; 

 plate I irregularly squarish; plate II slightly larger than I and 

 more distinctly squarish; plate III larger than II, IV larger than 

 III, V larger than IV, and all of these more or less squarish ; plate 

 VI broader than long, rounded and with spiracle in the middle; 

 plate VII very small, as broad as long. Legs rather short; femur 

 I, one and a half times as long as broad; tibia I about twice as 

 long as broad. Tubercle on femur III rather conspicuous and 

 well chitinized. 



Length of an average-sized, unengorged female, 2.75 mm.; width, 

 0.90 mm. 



Male. — Leg I enlarged as usual; first tarsal segment about as 

 broad as long, second tarsal segment about one and a half times as 

 long as broad. Chaetotaxy of thumb of tibia I (fig. 7) as follows: 

 Chief, or terminal, spine extending beyond margin of thumb by 

 less than half its length ; anterior accessory spine situated almost on 

 the inside of thumb, spinelike and somewhat longer than terminal 



