102 GENERAL ZOOLOGY 



that the bite of the mosquito is the only means of spreading 

 malaria, estimated that in India alone more than a million 

 persons die annually of this disease. But the outright deaths 

 are but a small part of the ravages of malaria. Dr. L. 0. 

 Howard of the United States Department of Agriculture 

 estimates that this disease in the United States alone is 

 responsible for a financial loss of not less than one hun- 

 dred million dollars each year. Yet malaria is doomed if 

 mosquitoes are exterminated. 



Yellow fever, which until the opening of the twentieth 

 century was one of the most dreaded diseases in this coun- 

 try, depended entirely upon the bite of the mosquito (Aedes) 

 for transmission. Dr. Reed with his coworkers, Carroll, 

 Lazear, and Agramonte, working in Cuba, discovered the 

 relations of mosquitoes to yellow fever. Dr. Reed, Dr. Car- 

 roll, and Dr. Lazear gave their lives directly or indirectly in 

 one of the most unselfish personal sacrifices in the interest 

 of mankind. The knowledge growing out of their experi- 

 ments has saved millions of lives, and today yellow fever 

 (Fig. 63) is entirely wiped out of the United States. 



The importance of understanding the relation of insects 

 to disease is now well acknowledged. Yellow fever had com- 

 pletely disappeared from the United States because of suc- 

 cessful campaigns against the mosquitoes transmitting the 

 disease before anyone knew what organism the mosquito 

 is responsible for carrying. Professor Noguchi, a Japanese 

 scientist working in this country, showed in 1918 that yellow 

 fever is due to an organism called Leptospira. 



In both malaria and yellow fever the disease germs un- 

 dergo a necessary part of their development in the body of 

 the mosquito transmitting them from one person to another. 



Typhoid fever and dysentery are two diseases which the 

 house fly is responsible for spreading. The germs of both 

 these diseases are very abundant in the intestinal wastes 



