156 
Biology of Pediculus 
humanus 
Period required 
for development 
from 1st st. L. 
to adult 
Temp. ° C. and 
other conditions 
Feeding 
Authority 
corjporis 
15-18 days 
not stated ... 
not stated 
Railliet, 1895, p. 827 
11 „ 
near body ... 
twice daily 
Warburton, 1911 
11-12 „ 
not stated ... 
not stated 
Fantham, 1912 
15 „ 
25-28° . ’ 
once daily 
Legroux, 1915, p. 470 
17 „ 
not stated ... 
not stated 
J eanneret -Minkine, 
9-10 „ 
35°, constant, 35 lice, 
twice daily 
1915, p. 825 
Sikora, vm. 1915, 
11-15 „ 
on person 
25°, constant, 4 lice 
99 99 
p. 523 
99 99 
8 „ 
on man’s arm* 
continuous 
Nuttall 
capitis 
18 „ 
not stated ... 
not stated 
Railliet, 1895, p. -825 
14-21 „ 
99 * * * * * * 
99 
Eysell, 1913, p. 47 
8- 9 „ 
on man’s armf 
continuous 
Nuttall 
* Felt cell method (p. 105). f Wristlet method (p. 107). 
With regard to corporis, Railliet (1895, p. 827) is the unacknowledged authority used 
by Eysell (1913, p. 48), who in turn is cited by Prowazek (i. 1915, p. 67); whilst Fasal 
(ii. 1915, p. 225) and Heymann (m. 1915, p. 253) cite Eysell also without acknowledgment. 
Fiebiger (vn. 1915, p. 645) appears to have borrowed Eysell’s statement that capitis 
developes in 14-21 days, and to have applied it to corporis. These authors therefore only 
require mentioning in so far as concerns their method of procedure. 
Relatively few authors mention the time that elapses between the 
different moults. Warburton states they moult every fourth day, but 
he left the number of moults in doubt. Swellengrebel (1916, p. 4) 
gives the duration of the 1st, 2nd, and 3rd larval stages as 7, 6, and 5 
days respectively, without stating the experimental conditions. 
The following records, which I have condensed and ordered for 
comparison, give much more accurate information on the subject; the 
timing starts from when the young larva had its first feed after 
hatching—Table A. 
Protocols showing (a) the variation in the moulting periods of indi¬ 
vidual lice, and ( b ) the effect of a low temperature in retarding or 
impeding development ( corporis )—Table B. 
A similar individual variation in the rate of moulting has been 
observed by me in capitis. 
The Act of Moulting. 
The act of moulting takes place in all stages in the following manner. 
The old skin splits longitudinally along the length of the thorax and 
forward to the heavily chitinized vertex of the head along whose edge the 
split extends laterally to near the base of the palps. The insect's head 
