24 LICE AND THEIR MENACE TO MAN 



the cap and is taken in by the insect at the mouth 

 and passed out behind it. As this increases a 

 growing cushion of air is formed in the bottom 

 of the shell which pushes the louse forward as a 

 bullet is pushed out of a rifle, though the move- 

 ment is slow. The head pressing against the 

 cap thrusts this up and the louse comes into the 

 world like a jack-in-the-box until its front legs 

 are free and it can grasp surrounding objects and 

 puU itself out (Fig. 7). 



FIG. 7. THE LARVA OF PEDIGULUS HUMANUS EMERGING FROM THE EGG. 

 The louse passes air through its body into the shell behind it and 

 thus blows itself out until it can grasp surrounding objects and 

 draw itself free. (After Nuttall.) 



The newly emerged louse is white and fragile. 

 Under ordinary circumstances it feeds within the 

 first hour of its active life and then looks like a 

 bright red speck and is very conspicuous. Unless 

 able to feed within the first twenty-four hours of 

 its life it dies. From the first it is easily recognis- 

 able for what it is, being much like its parents. 

 As a comparison, the larva which emerges from 

 the egg of a flea is a small white active grub, 

 nothing at all like the adult, which runs about on 



