128 
Biology of Pediculus humanus 
entomological boxes and they were afforded an opportunity of feeding 
through chiffon (covering the orifice of the box) during 6-7 hours in 
the 24. 
The number of eggs laid per day by a female. 
(a) Under natural conditions. There are only two observations to 
record from the literature under this heading. Leeuwenhoek (loc. cit.) 
allowed the two females with which he experimented to remain 6 days 
under the stocking on his leg, and found that they had laid 40 and 50 
eggs respectively during that period (average 6 and 8 eggs per day for 
each female). Wilder (1911, p. 87), like Leeuwenhoek, placed lice in 
a stocking, but he used a patient’s leg instead of his own; 70 with 
70 dd were left beneath the stocking for two days and during that 
period laid 1000 eggs (average oa. 7 eggs per day for each female). In 
both of these observations the period of observation was limited, so 
that the figures do not represent a true average, for the whole laying 
period. 
( b) Under artificial conditions. Warburton (loc. cit.) records of 
1 $ that she laid 124 eggs in 25 days under conditions already‘referred 
to (average 5 eggs per day). Fantham (1912, p. 514) following War- 
burton’s method (?) states that a female lays 4-5 eggs per day; Widmann 
(vm. 1915, pp. 292-293) saw females lay 5-6 eggs per day for 12-14 
days; Swellengrebel (1916, p. 12) gives 3 eggs as the daily average. 
The last three authors do not state the conditions under which their 
observations were made. Sikora (vm. 1915, p. 528), under conditions 
similar to Warburton’s, found that a female laid 2-4 eggs daily for 
3-4 days, then 5-7-8 daily; one female laid 20 eggs in two days; on 
the approach of death only 2-4 eggs were laid per day. Bacot (n. 1917, 
pp. 243-244), under conditions already described above, found that 
females laid 3-5-6-4 eggs per day, averaging 5-1 during the whole 
oviposition period; whilst during a limited period of 8 days ca. 5 
females laid an average of 4-5-6-S eggs per day. When they were given 
an opportunity of feeding for ca. 10 hours instead of 5-6 hours out of 
the 24, they laid an average of 8 eggs per day during a period of 8 days. 
Finally, I append the result of an unpublished observation by 
Mr L. Harrison in my laboratory. He fed 10 twice a day and 
maintained them isolated with as many males, at 30° C. in the ther¬ 
mostat between meals. During a period of 10 days they laid a total 
of 312 eggs, the averages per day per female ranging from 1-9 to 4-1. 
98 records of the number laid per day by each female show that 8 eggs 
