18 



made. Even the common bedbug (fig. 15) is strongly suspected in 

 this connection. 



YELLOW FEVER. 



One of the most important of these disease-transfer relations of 



insects which has been 

 demonstrated is the car- 

 riage of yellow fever 

 by certain mosquitoes. 

 The cause of yellow 

 fever has always been a 

 mystery, and indeed it 

 is a mystery to-day in 

 a measure, since, al- 

 though undoubtedly a 

 disease of parasitic 

 origin, t h e parasitic 

 organism itself has not 

 yet been discovered. 

 During the summer and 

 autumn of 1900 and 

 spring and summer of 

 1901 the work of a com- 

 mission of surgeons of the United States Army demonstrated in 

 Cuba beyond the slightest possible doubt that yellow fever is not 

 conveyed by infected clothing of yellow-fever patients or by contact 



Fig. 13. — Tsetse 



Enlarged (original). 



Fig. 14. — Black gadfly. Enlarged (ori- 

 ginal). 



Fig. 15. — Bedbug. Enlarged (after Mar- 

 latt). 



with such patients or by proximity to them, but that it is conveyed 

 by the bite of a certain species of mosquito known as Stegomyia 



155 



