HABITS OF AEDES CALOPUS 



447 



will not live beyond 50 days, but the females frequently live 

 under laboratory conditions for four months or more. Kind 

 of food, dryness of climate and facilities for laying eggs are among 

 the chief factors determining the length of life of these mosquitoes, 

 and, strange as it appears at first, 

 the length of life is shortest under 

 the most favorable conditions, 

 namely, plenty of blood for food, 

 plenty of moisture, and suitable 

 places for egg-laying. 



The flight of the yellow fever 

 mosquito is strong but, like most 

 other mosquitoes, it seldom flies 

 long distances, usually not more 

 than a few hundred feet. Vessels 

 lying half a mile from shore rarely 

 if ever are visited by these mosqui- 

 toes unless the latter are carried 

 from shore by lighters or boats. Fia. 205. Pupa of yellow fever 



Owing to its domestic habits S^tblfarTndTnabf "^ '^''" 

 and its ability to " stow away " 



the yellow fever mosquito has been, and annually is, widely 

 distributed over the world. As pointed out by Howard, Dyar and 

 Knab, its original home was very probably tropical America, 

 since the evidence points to the origin of yellow fever in the 

 West Indies and neighboring mainland, and it is inconceivable 

 that the parasite of this disease would have developed in any 

 other region than the original home of its obligatory host. The 

 permanent home of this mosquito is now almost the entire warm 

 portion of the world, wherever a temperature of 80° or more 

 is maintained for any length of time, and where freezing does not 

 occur. The once common occurrence and breeding of this mos- 

 quito during summer months in cities of the Atlantic Coast of 

 the United States and in other ports outside the frostless zones was 

 due to its importation on ships from such infested cities as New 

 Orleans, Havana and Rio de Janeiro. The cool nights and low 

 summer temperatures on the Pacific Coast of the United States 

 prevents its thriving there, in spite of the fact that it is still some- 

 times carried there on ships. Since the practical extermination 

 of this mosquito in most of the ports where it was once abundant 



