68 THE FLEA [CH. 



the rostrum is longer and the clasper of the male is 

 more pointed. If the Mexican Indians have a special 

 race of human flea it must have developed after the 

 Indians came to America, or they must have brought 

 it with them when they came. In the latter case this 

 race of flea may still exist in the country whence 

 these Indians originally came. 



Apart from this apparently constant race, the 

 individual variation in specimens of the human flea 

 is slight. If a large series of mounted specimens are 

 examined with the microscope, it will be noticed that 

 the bristles or spines on the legs are sometimes more 

 or less numerous. But, with this exception, marked 

 varieties such as are frequently found among other 

 insects seem to be rare. 



Although mankind is the true host of this flea, it 

 has been obtained in various parts of the world on 

 various mammals and occasionally on birds. But in 

 England, and probably in other parts of Europe as 

 well, Pulex irritans is an undoubted parasite of the 

 badger. A good series of the insect has been got 

 from wild badgers freshly captured near Reading in 

 Berkshire and Hastings in Sussex. In other parts of 

 the world it has been obtained from a variety of small 

 carnivora: cats, dogs, foxes, jackals and polecats. It 

 has also been found on Rodents (Gerbillus) and on 

 Insectivora (Erinaceus). In South Africa it has been 

 taken off a caracal and in North America off a lynx. 



