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A CONTRIBUTION TO THE BIONOMICS OF 
PEDICULUS HUMANU8 {VEST13IENTI) AND 
PEDICULUS CAPITIS. 
By k. BACOT, 
Entomologist to the Lister Institute of Preventive Medicine. 
In its inception this work was planned with a view to supplement 
our present knowledge of the life history of Pediculus humanus [vesti- 
menti, which we owe so largely to Warburton^ (1909). The scheme 
was to work out in detail certain problems relating to sex and fertility 
and incidentally to obtain further evidence in support of what is already 
known concerning the laying and hatching of eggs. The success of an 
attempt to breed P. capitis under conditions that had already proved 
satisfactory with P. humanus suggested that it was worth while enlarging 
the scope of the scheme in order to include the head louse, as this insect 
seemed to be amenable to the same conditions of captivity. 
These conditions, as nearly natural for P. humanus as were consistent 
with captivity and isolation, are admittedly more artificial when applied 
to P. capitis ; it is necessary to keep this fact in mind when comparing 
the bionomics of the two insects as described in this paper. 
The lower egg production of capitis is in all probability chiefly 
due to the smaller egg-containing capacity of its body; for, in spite 
of the fact that the eggs of the head louse are slightly smaller than 
those of the species associated with clothing, the body extension of 
the ?? P. humanus still gives them a marked advantage with respect 
to the number of fully developed eggs that they can carry. The shorter 
life, and apparently lower vitality of P. capitis as compared with P. 
* I was unaware of the publication of Sikora’s (1915) excellent paper, which contains 
much fuller details than any hitherto publi.shed account of the biology of P. humanus 
{vestimenti), until the experiments detailed in this paper had been mapped out and half 
completed. 
