252 ENTOMOLOGY 



while those of Anopheles are almost parallel with the surface of the 

 water in which they live. 



The bite of an Anopheles is not necessarily injurious, of course, unless 

 the insect has had recent access to a malarious person. Anopheles may 

 be present where there is no malaria. On the other hand, it has been 

 found impossible to prove that malaria exists where there are no Anoph- 

 eles mosquitoes. Finally, fevers are sometimes diagnosed as malarial 

 which are not so. 



Possibly the malarial parasite can complete its cycle of development 

 in other animals than man. It is also possible that originally the mala- 

 rial organism was derived by mosquitoes from the stems or other parts 

 of aquatic plants, and that its effects on man are incidental phenomena. 



YELLOW FEVER 



From 1793 to 1900 there occurred in the United States not less than 

 half a million cases of yellow fever and one hundred thousand deaths 

 from the disease. New Orleans suffered the worst with more than forty- 

 one thousand deaths, followed by Philadelphia with ten thousand and 

 Memphis with almost eight thousand; while Charleston, New York 

 City and Norfolk, Virginia, lost together more than ten thousand lives. 



The enormous financial loss from all the epidemics of yellow fever is 

 beyond exact computation; the epidemic of 1878 cost New Orleans more 

 than ten million dollars. 



Yellow fever is now within human control; with no thanks to those 

 who at first violently opposed the theory, and later denied the fact, of 

 its transmission by mosquitoes. 



Until 1901 yellow fever was fought energetically, but fought in the 

 dark. An immense amount of energy was misdirected and millions of 

 dollars wasted in the fight. On the supposition that bacteria were the 

 cause of the disease, methods of quarantine, burning and fumigation 

 were employed that destroyed an enormous amount of property includ- 

 ing valuable cargoes, and paralyzed the business and social activities of 

 great cities. 



Official accounts of yellow fever published before 1900 often describe 

 the disease as being due to some insidious poison borne by the air and 

 introduced into the human body, probably through the respiratory 

 system. It was observed that the disease was often conveyed down 

 the wind, that it was not carried far from the nearest focus of infection, 

 that infection was less liable to occur in daylight than by night, and 



