642 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



The organism causing yellow fever is not known, but it is known 

 by absolutely conclusive experimental evidence which has been 

 demonstrated on a large scale, that a mosquito, (Aedes calopus) is 

 the sole means of the transmission of the disease from a yellow 

 fever patient to a healthy person. Soon after this was proven it 

 was demonstrated. The city of Havana and the Panama Canal 

 Zone, long centers of infection for the fever, were, by a vigorous 

 campaign, freed from mosquitoes. Yellow fever, never known to 



FIG. 558. Dorsal view of the 

 iarva of a malarial mosquito, 

 Anopheles. After Smith, New 

 Jersey Agr. Expt. Sta. 



Fia. 559. The yellow-fever 

 mosquito; larva. Much en- 

 After Howard, U. S. 

 Dept. of Agr. 



be absent in those regions, was thereafter almost unknown. Other 

 cities have since followed these examples and the control of the 

 once dreaded disease is merely a matter of thoroughness in ridding 

 the localities of mosquitoes. Similar measures result in the 

 lessening or disappearance of malaria. 



Mosquitoes breed in water, usually stagnant. The larvae are 

 the common wrigglers which used to be summer residents of every 

 rain-barrel. The pupae are sufficiently illustrated in the illustra- 

 tions, so they need no description. 



Many species of mosquitoes are not known to carry diseases 

 but are of extreme importance since, on account of their biting 

 habits and tremendous numbers, they render large tracts of country 



