G. H. F. Nutt ALL 
403 
tube containing hot water is brought near them whilst feeding, but 
otherwise they “become greatly excited and move with remarkable 
eagerness and rapidity,” and if placed on their backs on a table and a 
hot tube approaches them, their “wild efforts to reach it attain an 
intensity which is almost pathetic.” 
Although the pubic and peri-anal and axillary regions are the sites 
of selection for its parasitism, there is no evidence that these habitats 
are chosen because of their higher temperature and moisture. The 
selection of these regions seems to depend only upon the character of 
their hairiness. 
Summary and Conclusions. 
Although Phthirus pubis occurs in Europe, Asia, Africa, North 
America and Australia, and is found on negroes as well as whites, as 
herein recorded, further data are required relating to the geographical 
distribution of the species and the races of man it infests. 
The crab-louse occurs less frequently on man than does Pediculus 
and appears to be parasitic chiefly on persons leading an active sexual 
life. It has, so far, only been twice recorded on another host than man, 
i.e. the dog. 
Whilst the crab-louse is usually found confined to the pubic and peri¬ 
anal region, it frequently spreads upward upon the abdomen and breast, 
and may infest the axillae severely, or it may spread downward along 
the thighs. Generalized infestation is rare, in such cases only the hands 
and feet are spared, although the head and neck are as a rule also free 
from parasites. The crab-louse has occasionally been found localized 
upon the head in infants, being either confined entirely to the eyelids, 
the nits being encountered on the eyelashes, or occurring also upon the 
eyebrows and hairy portions of the scalp. In adults, the parasite occurs 
much more rarely in these situations; a case is recorded of an Arab in 
whom, in addition, the beard and moustache were infested. Such cases 
are rare in children, very rare indeed in adults. 
Apparently the head is so rarely infested because it is less suitable 
as a habitat. As Waldeyer points out, the head is probably not a suit¬ 
able habitat because the scalp-hairs are crowded close together and finer 
than on the pubis and in the axillae. The majority of the active stages 
are found clinging to two hairs on the regions of the body they most 
infest, and where the hairs are sparser than on the head. In these parts, 
the hairs are 2 mm. or more apart. The reach between the extended two 
