Cl. H. F. Nutt all 
217 
Conclusions. 
Section {a). 
The most darkly pigmented capitis are derived from dark-skinned black¬ 
haired peoples. Head-lice tend to grow paler on yellow or moderately pale 
races possessing black hair. The palest head-lice are found on white races 
whose hair is often light in colour. 
Whilst the darkest corporis are obtained from negroes, the insects in most 
cases cannot be grouped according to the skin colour of the host. The occur¬ 
rence of pale body-lice on dark-skinned races is doubtless attributable to their 
wearing white or light coloured clothing especially in hot countries. 
Phthirus pubis derived from negroes are darkly pigmented, whereas those 
derived from whites are pale for the same reasons that apply to head-lice. 
The statement that lice may change colour when transferred from light 
to dark races and vice versa (Murray, Bodkin), in the absence of experiments 
on man, finds support amounting to confirmation in the experiments herein 
described wherein lice were raised on differently coloured, black, and white 
backgrounds. 
It appears highly probable that paler head-lice will be obtained from light¬ 
haired than from dark-haired individuals among white races. I am at present 
collecting data in this connection and shall be grateful to any readers who may 
supply specimens or further information on the subject. 
Note. The paper by Sikora (ix. 1917, pp. 278-279) has come to hand whilst 
this publication is going through the press. According to Sikora, capitis 
derived from black-haired persons are not always darker than those found 
on individuals with moderately fair hair, but the very fair haired always 
harbour distinctly paler lice. The contrast in the pigmentation of such lice 
is never so great as in the insects raised experimentally on black and white 
respectively. A very blond girl, bearing many pale head-lice, also harboured 
a few dark lice which were evidently derived from her (verminous) dark¬ 
haired mother. 
Section (b). 
The experiments detailed in this section show: 
That pigmentation in lice is dependent upon the nature of the background 
upon which the insects are raised. If eggs laid by dark lice on white cloth are 
allowed to hatch and develope on white cloth, they will appear pale in all 
stages from the first larva to the adult (Expts. IV, V). Conversely, if eggs 
laid by pale lice on black cloth hatch and the insects be raised on black cloth, 
they will appear dark in all stages. Lice raised on a gray background show 
various degrees of pigmentation that are intermediate compared with the 
results obtained on black and white (Expt. II). It is immaterial if the pill¬ 
boxes in which the lice are raised are black or white externally (Expt. IV). 
The darkest lice were obtained in boxes blackened inside and containing black 
cloth, they were mostly less dark in boxes that were white inside and contained 
