Photo: J. J. Ward. 



FEMALE FLEA OF RAT (Magnified 50 diameters.) 



The flea is a wingless insect, with great powers of leaping, as the length of the legs suggests. Unlike 

 most insects it is much taller than it is broad. The male is much smaller than the female. The eggs are laid 

 in crevices, and there the metamorphosis, through larva and pupa stages, is accomplished. The larva eats 

 fragments of organic matter. When an adult flea bites man it injects a secretion from its mouth, and this sets 

 up irritation. But the piercing mouth-parts may have been contaminated with microbes, and these increase 

 the irritation or may produce disease. Thus when the rat-flea of warm countries has been biting a rat whose 

 blood contains the bacillus of the plague, it may proceed to bite man and infect him. 



