PUBLIC HEALTH 5 



they impair its efficiency by enfeebling the health of its hu- 

 man population. Their direful influence is more pronounced 

 in the tropics, whence it has been most commonly pro- 

 claimed, but our own country is by no means exempt, al- 

 though its cooler climate causes it to be less severely affected. 



No other insects can compete with the mosquitoes as per- 

 sistent annoyers of man, and none, with the possible excep- 

 tion of the rat-flea, hold over him such power for evil. Practi- 

 cally no part of the globe that can serve for human existence 

 is free from mosquitoes, and large areas from the tropics to 

 the arctic are periodically invaded by them in varying abun- 

 dance. Even where irrigation has made the " desert blossom 

 like the rose" it has often also produced a crop of mosquitoes 

 to annoy or even afflict with disease the inhabitants of the 

 garden. 



On account of their phlebotomic habits, and particularly 

 their fondness for man, mosquitoes have always been heartily 

 detested, even by the entomologist, and only their known 

 association with human diseases has brought them to the 

 serious attention of zoologists. With this incentive, however, 

 a vast amount of work has been done by entomologists and 

 medical men and an enormous mass of literature has been 

 produced in less than two decades, bearing on every con- 

 ceivable aspect of the subject. We now know that mosquitoes 

 are responsible for many deaths, much human misery and 

 great economic loss through their activity as disseminators 

 of malarial fevers, yellow fever, dengue fever, filariasis, etc. 



In all of this, several of the more important relations of 

 mosquitoes to public health stand out very clearly. They are: 

 (1) Some very important diseases of man are transmitted by 

 certain specific mosquitoes, the latter being absolutely 

 necessary for the continued existence of these diseases. (2) 

 The disease-bearing mosquitoes are most widely distributed 

 in the tropics, whence they extend into portions of the tem- 

 perate zones. (3) The range of mosquito-borne diseases is 

 not necessarily coextensive with the distribution of their 

 insect carriers, but is dependent upon other factors as well. 



