14 INSECTS AND HUMAN WELFARE 



necessary for the development of a possible epidemic in a 

 region where Stegomyia occurs is the introduction of a human 

 case in the early stages of the fever. 



The larval habits of Stegomyia are in quite marked con- 

 trast to those of Anopheles. The adults are strictly domestic 

 mosquitoes and occur almost entirely in the neighborhood of 

 human habitations. Their larvae occur in the same places, 

 breeding preferably in vessels containing small amounts of 

 water, rain barrels, cisterns, stray tin cans filled with rain 

 water, etc. On this account, extermination work against the 

 yellow-fever mosquito resolves itself mainly into the exami- 

 nation and treatment of cities, towns, and the immediate 

 environs of smaller settlements. 



A Stegomyia feeding upon the blood of a person suffering 

 from yellow fever becomes infected only during the first three 

 or four days after the onset of the fever; later than this mos- 

 quitoes do not obtain the virus. An incubation period of at 

 least twelve or fourteen days in the mosquito is now necessary 

 before the mosquito can infect a second person, after which 

 the Stegomyia remains infectious for a long period and may 

 be responsible for a series of new cases. These facts were first 

 discovered during the summer of 1900 hy a Yellow Fever 

 Commission consisting of Drs. Reed, Carroll, Lazear, and 

 Agramonte, of the U. S. Army. Two of these men, Carroll 

 and Lazear, allowed themselves to be bitten by infected 

 mosquitoes. Lazear died from a severe case of fever con- 

 tracted during the course of the experiments, and Carroll 

 nearly succumbed to a severe case following the bite of an 

 experimentally infected mosquito. 



Little further has since been learned of the etiology of 

 yellow fever, but wonderful strides have been made in the 

 application of these simple facts for its eradication. In Cuba, 

 where the commission conducted their investigations, the 

 first attempts were made, and in 1902 yellow fever had been 

 entirely eliminated in Havana. Other West Indian islands 

 were formerly badly infested with yellow fever, but at the 

 present time there is little more danger from this disease 



