144 
Biology of Pediculus humanus 
53 days (Nut tall); 15° C. (Hindle and Harrison mss.); 16° C., constant 
(Sikora 1 ); 15-6-18-4 0 C., dry, observation period 24 days (Bacot 2 ); 
6-10° at night and 20° C. by day (Sikora 1 ); 12-20° C., observation 
period 21 days (Hase 3 ); 22° C., observation period 54 days (Nuttall); 
22° C. (Hindle MS.). 
The observations recorded by the following authors are therefore 
erroneous, namely, that eggs hatch at 20° C. in 7 days, tested on 
3 eggs (Widmann 4 ); at 20° C. in 10-12 days (Heymann 5 ); at “room 
temperature” in 4-6 days (Wulker 6 ); at 16-18° C. “they rarely hatch” 
(Legroux 9 ). 
The following table records the observations of different authors, 
arranged in accordance with the temperatures at which the eggs were 
maintained prior to hatching'being observed: 
Temperature at which 
eggs were kept, ° C. 
Eggs hatched after 
Authority and remarks 
After 13 days at 10°, they 
were placed at 26-30° 
After 2 days at 0°, they 
10 days 
Widmann 1 (6 nits) 
were placed at 26-30° 
13 „ . 
„ (5 nits) 
25°, constant 
ib ,, . 
Sikora 1 
25-28° . 
8-10 days 
Legroux 9 (saidtobe optimum) 
25-30° . 
8-10 „ ... . 
Hase 3 
28°. 
61-7 „ . 
Widmann 4 
28°, damp ... 
7 days 
Nicolle, Bla-izot and Conseil 7 
? 28° . 
7-15 days, mostly 11-15 days 
Swellengrebel, 1916, p. 4 
30°, constant, dry 
7-14 days, mostly 11-13 days 
Nuttall 
In coat pocket 
8 days 
Nocht and Halberkann 8 
32°, constant, dry 
7-8 days usually 
Nuttall 
In tube near body 
8 days 
Warburton, 1911, p. 25 (8 
nits) 
35°. 
71 „. 
Widmann 4 (3 nits) 
35°, on man’s body 
6 „. 
Sikora 1 
ca. 35°, on man’s arm 
7 „. 
Nuttall (the first of many) 
In stocking on leg 
6-8 days 
Wilder, 1911, p. 87 (many) 
Near the body 
5 days... 
Nocht and Halberkann 8 
In bag under armpit 
6-8 days 
Peacock, 1916, p. 39 (6 nits) 
36-1°. dry . 
4-8 „ . 
Bacot 2 (143 hatched) 
37°, damp ... 
5-6 „ . 
Nocht and Halberkann 8 
37°. 
5-7 days, rarely 5 days 
Hase 3 
37°, dry, constant 
4-7 days, mostly 5-6 days ... 
Nuttall 
38°. 
8 days 
Widmann 4 
40-45° . 
died 
Sikora 1 
1 Sikora, vm. 1915, p. 529. 2 Bacot, n. 1917, p. 248. 
3 Hase, 1915, p. 22, cited 
by Muller, 1915. 4 Widmann, vm. 1915, p. 293. 5 Heymann, 18. vm. 1915, p. 305. 
6 Wulker, 1915, p. 628. 
7 Nicolle, Bla-izot and Conseil, 
1912, pp. 110-192; vn. 1912, 
pp. 1636-1638. 8 Nocht and Halberkann, 1915, p. 626. 
9 Legroux, 1915, p. 470. 
