Marvels of the Universe 
host, its safest policy is to remain on the track 
until the hedgehog returns (for it runs over its 
track many times throughout the night), when, 
I have no doubt, it can jump quite well. 
That, I think, is the explanation of the hedge- 
hog flea’s peculiar habit. I may also add that 
I do not think the hedgehog flea will migrate 
to man. 
The flea of the fowl presents another example 
of a flea which does not leap; it, however, 
runs swiftly. 
The body of these degenerate insects has, 
likewise, become marvellously adapted to their 
requirements. It is clothed in a suit of mail, 
perfect in fit and rhythmic in action. Its 
horny segments are provided with bristles all 
pointing backwards, and it is these bristles, 
combined with its smooth 
account for the flea’s extraordinary power of 
slipping through closely-pressed fingers ; for, if 
it can only wriggle forward, these bristly seg- 
ments prevent it from slipping back again. Also 
the body is laterally compressed, being so flat 
that it can bear enormous pressure on the soft 
body of its victim without ill effects. This com- 
surface, which 
797 
Photo bu] [J. J. Ward, F.ES. 
THE HEAD AND SHOULDERS OF THE FLEA. 
Notice the bristles which fringe the hinder rim of each segment. 
They point backwards and prevent the insect from slipping. 
pression of the body is common to many forms of animal parasites, but the fleas are remarkable 
for their lateral flattening, for, as shown in the illustrations 
Parasites,” the bodies of most other 
forms of parasites are compressed 
from above and below. 
On the terminal segment of a 
flea’s body the curious 
organ known as the “ pygidium.” 
This is a most extraordinary piece 
of mechanism when seen _ highly 
magnified, being provided with 
disc-like orifices from which arise 
long sensitive bristles. It is very 
doubtful what function 
this organ serves, but it has been 
is seen 
‘ 
sensory 
shown with some probability that 
it represents the flea’s auditory 
apparatus. 
It now remains to consider the 
head of the flea, for in this part 
of its anatomy are contained the 
weapons with which it inflicts its 
so-called “ bite,” which is really 
a minute puncture opened by a 
Photo bu] 
of my previous article on “ Bird 
[A. Banfield. 
THE MALE HUMAN 
The body of the Flea is laterally compressed, and this flatness enables it 
FLEA. 
to bear enormous pressure without hurt. 
