THE FLEAS OF NORTH AMERICA 117 



Baker originally described dugesii as a variety. Later (1904) he 

 raised it to the rank of species, stating : 



First described as a variety of irrilans, this form is now given the rank of a 

 species. The examination of a large series shows the characters to be uniform 

 and thoroughly distinctive. 



An examination of the type specimens of dugesii by the writers in- 

 dicates that, except for the longer labial palpus, it agrees fairly well 

 with irritans. Hence it is given only the status of a subspecies in 

 this paper. 



Pulex irritans irritans Linnaeus 



Pirfe.r irritans Linnaeus, 1758, Systema Naturae, ed. 10, p. 614. 

 Pulex simulans Baker, 1895, Canad. Ent. 27: 65. 



Type host.— "Man." 



Type locality. — Sweden ( ? ) . 



Range. — Of all the species of fleas, Pulex irritans is probably the 

 most nearly cosmopolitan in distribution. Yet there are good reasons 

 for not regarding it as truly cosmopolitan. It is now established in 

 all the major zoogeographical regions, yet there is evidence that it 

 does not occur in many wild areas uninhabited by man, and in addition 

 it probably is absent or extremely rare in certain large cities. 



Jordan and Rothschild (47, p. 9), in 1908, said regarding irritans: 



* * * Our knowledge of the variation and the present and former distribu- 

 tion of this insect is extremely meagre. 



They stated : 



* * * The nearest allies of this species which are found on various animals 

 are all inhabitants of the Old World. The fleas found in America are only 

 distantly related to P. irritans. It may therefore be concluded that the present 

 species originated from the Old World stock of Siphonaptera. 



This statement was made a long time ago. Since then Juxtapulex 

 porchius (Jordan and Rothschild) and J. echidnophagoides Wagner 

 have been described from native hosts in the New World, the former 

 being originally placed in Pulex. In view of these discoveries the 

 present writers are of the opinion that Pulex, as well as Juxtapulex, 

 was originally an American genus, and that it was in the New World 

 that P. irritans originated. 



The apparent absence of Pulex irritans in certain regions of the 

 Old W x orld was noted by Jordan and Rothschild (Ifl, p. 9). They 

 state that — 



The tropical countries of the eastern hemisphere do not appear to be inhabited 

 by P. irritans except where European settlements exist, or, at least, where 

 intercourse with Europeans goes on. * * * 



The absence of Pulex irritans from the oases of the Sahara and from the 

 Haussa countries south of the Sahara appears to be a well-established fact. 



The distribution of Pulex irritans in the United States has been 

 especially considered by Ewing (IS, p. 363) , who stated in 1931 : 



* * * The unusual thing about its distribution has to do rather with its 

 sparseness in certain large areas than its absence in them. . Yet certain areas 

 exist in which repeated search for this flea has failed to reveal its presence. 



These areas are chiefly wooded regions not inhabited by man. They 

 probably are free from infestation because of the absence of true 



