INSECTS AS AGENTS IN SPREAD OF DISEASE 543 



Anti-malarial work of this sort has been undertaken and success- 

 fully prosecuted in many parts of the world; in the Federated Malay 

 States, in the Suez Canal region, at Havana, Cuba, and in the Panama 

 Canal Zone. Many other regions might be mentioned, but we must 

 look in vain for such concerted and sustained work in the United States. 

 Attempts have been made by many entomologists and public-spirited 

 citizens to inaugurate measures against mosquitoes on account of their 

 relation to malaria, but with the excepion of the most successful work 

 accomplished by Smith in New Jersey and by others on Long Island 

 little has been done to aid the efforts of the energetic few. We have, 

 however, reason to believe that such apathetic contemplation on the 

 part of the American public will some day develop into an active 

 interest, and that the population of our extensive malaria-ridden areas 

 will gradually see the possibilities of improvement in public health 

 through the destruction of the malarial mosquito. 



Another mosquito-borne disease which has aroused more interest in 

 America on account of its spectacular appearance and higher mortality 

 is yellow fever. This is due to a filterable virus, concerning the nature 

 of which we can only speculate at the present time, although enough 

 has been ascertained through experimental work to demonstrate that 

 the virus is a living organism which undergoes a development of definite 

 periodicity in mosquitoes of a single species known as Stegomyia 

 calopus. This mosquito enjoys a very wide distribution in many parts 

 of the world, mainly in the tropics, but also extends into the warmer 

 temperate regions. Yellow fever is not so extensively distributed, being 

 absent in many places where Stegomyia occurs, but it is nevertheless 

 present in many parts of the tropics in both hemispheres and all that is 

 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 contrast 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 examination and 

 treatment of cities, towns and the immediate environment 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 mosquitoes 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 



