132 
Biology of Pediculus humanus 
% 4 
and 21st-22nd day. During the first 12 days 3 laid roughly 1, 4, 6, 
5, 6, 7, 7, 7, 6, 7, and 9 eggs apiece; during days 13-16 two $2 laid 
about 8, 7, 5, 7 eggs apiece; and during the following 5 days the 1 $ 
laid an average of 5 per day. It is unfortunate that the adults did not 
live longer. Their early death is attributed by me to the advent of 
warm weather. Although in a sense a failure, this experiment is of 
interest in its bearing on what is stated on pp. 87-90 regarding the 
seasonal incidence of lice. A further trial of the wristlet method of 
raising capitis during cooler weather is in contemplation, as it seems 
reasonably certain that it will yield a larger total of eggs, the adults 
living longer. 
The Preference shown by Corporis for Laying on Certain Fabrics. 
That lice prefer certain fabrics to others as a habitat has been 
repeatedly stated. Thus Hase (cited by Muller, 1915, p. 72) is reported 
to have made observations showing that they prefer rough felt-like 
woollen fabrics, and, next in order, loosely woven cotton and flannel; 
tightly woven linen, cotton, and silk being avoided unless no other 
fabrics are available. Hase (1915 a cited by Friedmann, 1916, pp. 
321-338) is also stated to have shown that lice definitely object to silk, 
since, under otherwise similar conditions, they lay eggs on wool in 24 
hours but only after some days on silk. Friedmann (1916, p. 325) 
placed lice in dishes containing strips of various fabrics and reported 
that the insects always sought wool in preference to silk; and, given 
the choice between silk and wool, they always oviposited on wool. 
In view of these statements it appeared desirable to make further experi¬ 
ments. 
To test the behaviour of female lice with regard to their preference 
for certain fabrics to the exclusion of others for the purpose of oviposi- 
tion, a simple mode of "experimentation was devised. Pieces of the 
different fabrics to be tested were cut of uniform size (ca. 2-5 x 1 cm.) 
and laid radially, like the numbers on a watch dial, upon the floor of 
a glass dish 10 cm. in diameter.. The pieces of fabric were surrounded 
on all sides by an area of glass. The lice,*after being fed, that is, twice 
a day, were put in the centre of the dish upon the glass, whence they 
wandered about at will in the darkness of a thermostat maintained 
at 32° C. 
Expt. 1. Four females with males were placed in the dish with 
five pieces of fabric. After 72 hours they had laid 
