114 
Biology of Pediculus humaiius 
Part III. 
SPECIAL BIOLOGY. 
The Relative Numbers of Males and Females in P. humanus. 
A few authors have noted that there appear to be more females than 
males present upon the infested host. For instance Harding (1898, p. 95) 
states this of capitis, and Sikora (vm. 1915, p, 528) of corporis. To 
my knowledge no actual enumerations have been made hitherto of all 
the lice or of an adequate number collected from persons with a view 
of determining if this is merely a subjective impression or not. Per¬ 
sonally I believe that many' males, especially when small, may be mis¬ 
taken for third-stage larvae and thus lead to a false impression of their 
numbers. Moreover, when specimens are collected by inexperienced 
persons or assistants, there is a natural tendency to collect the largest 
specimens, most of which are likely to be females. 
As yet, I have only been able to make one enumeration of what 
constituted practically all the capitis that were present on one person. 
The specimens were taken from a woman’s head which was shorn in 
my presence. By a curious coincidence there were exactly 104 d and 
104 $ present upon the scalp. It is evident that further enumerations 
of the kind, both of capitis and corporis, are required to determine the 
proportion of the sexes upon the host, since this observation is in direct 
contradiction with what has hitherto been stated. In any case, Sikora’s 
explanation that the females appear more numerous because they live 
slightly longer, is one that scarcely throws light on the problem. 
Raising Experiments. 
The proportion of the sexes, as determined by raising experiments, 
has yielded contradictory results. Owing to the marked disparity in 
the proportion of the sexes constituting the broods of certain pairs, 
as first discovered by Hindle (n. 1917, p. 259), the figures obtained are 
specially liable to fallacious conclusions when these are based on limited 
observations. Mr Harrison has calculated from Idindle’s MS. notes, 
that the latter raised (from 1590 first stage larvae) a total of 944 corporis 
to maturity of which about 40 % were d and 60 % $, the actual 
numbers being 392 d and 552 ?. These figures would tend to support 
the view that the females are more numerous than the males. On the 
other hand, if we total up the progeny of Bacot’s hybrids ( vide infra) 
