292 The Control of Mosquitoes 



gard to the reintroduction of the disease at some 

 future time. 



When the reduction of Aedes calopus has 

 reached a certain stage, the chance of a person 

 being bitten becomes so small that transmission 

 of fever stops. Yellow fever was eradicated 

 in the epidemic at Havana, Santiago, and other 

 towns and villages in Cuba, as well as in the Canal 

 Zone and the cities of Panama and Colon, when the 

 number of Aedes calopus present was much higher 

 than now. Since the last case of local origin in 

 1906, on several occasions imported cases have 

 gained access to, and actually been at large in 

 Panama and Colon, without producing secondary 

 cases; because the number of adult Aedes calopus 

 is so small that there are almost no chances of 

 completing the chain necessary for the transmis- 

 sion : a patient being bitten, this particular insect 

 surviving twelve days, and then biting a non- 

 immune. In some settlements in the Canal Zone 

 Aedes calopus are now seldom seen. 



It must be remembered, however, that but a 

 short time is needed to reintroduce this species 

 of mosquito, and that if conditions are allowed to 

 become favorable, it will both multiply and spread 

 over a populated area with great rapidity. 



