134 
Biology of Pediculus humanus 
The colour of the fabrics exerted no influence, for the insects were 
kept in the dark. The essential factor governing selection is apparently 
the texture of the fabrics, the ones selected being those affording the 
best foothold combined with interstices and irregularities of surface 
and especially the presence of numerous fibres to which and amongst 
which the eggs can easily be cemented. Felt and flannelette were 
the most preferred, whereas silk is by no means avoided; in fact silk 
tricot stands second on the list. Smooth materials are as a rule not 
selected, but lice will lay even on black sateen and smooth silk, espe¬ 
cially when choice is limited. 
The Number of Eggs Laid on Hair as compared to Cloth by 
Corporis and Capitis. 
\ 
That clothes-lice may lay on hair was first recorded by Sikora 
(viii. 1915, p. 524); although I had established this before in experi¬ 
ments with artificial scalps made of hairs planted in hard paraffin 
and had found eggs laid on hair most convenient for testing the effect 
of insecticides upon them. 
Bacot’s Observations. 
The statement of Bacot (n. 1917, pp. 231-232) that corporis and 
capitis behave differently, when given a choice between cloth and hair 
upon which .to oviposit, is of interest as indicating a biological difference 
between them. 
According to Bacot corporis seldom if 'ever lays eggs on hair if cloth 
is available: (1) In one experiment, 2 or 3 $$ were confined in a 
breeding box containing hair 2-3 cm. long, but no cloth; during a 
period of 3 days they laid 35 eggs of which 21 were attached to two or 
more hairs, especially (in 60 %) where hairs crossed each other; 4 were 
fixed to single hairs; 9 were fixed to the gauze cover, and 1 was attached 
to the hairs and box. (2) In a second experiment with flannel and 
hairs contained in a box, the females laid 44 eggs on flannel and 56 eggs 
on hair; Bacot refers this result to the matted arrangement of the 
hairs in the box. Bacot subsequently reported (iv. 1917, p. 63) 
that when corporis are given a choice between flannel and hair, they 
will lay 80 % of their eggs on flannel. He gives the protocols of two 
experiments (III, IV) made with two lots of 12 ?? in a box containing 
flannel and hair. Box (A) contained females bred from eggs laid on hair, 
and box (B) such as had been raised on flannel. The result, after five 
days, was as follows: 
