I 



Proceedings of Fieth Annual, Meeting 107 



cause oe mosquito flight 



The cause of mosquito migrations is obscure, but it is safe to 

 assume they are in some way related to one or both of the great 

 necessities of living matter — ^persistance of the individual and 

 the reproduction of its kind. 



The mosquito emerges, its body wall hardens, its parts be- 

 come adjusted, and it flies away in search of food and opportuni- 

 ties for reproduction. Usually these desired conditions are found 

 nearby. The female alternates between places where food may 

 be had and places where eggs may be laid. 



This is the type of movement exhibited by the mosquitoes that 

 breed about human habitation (the house mosquito) and the 

 underlying causes are very evident. 



When the same species breeds very intensely on a very large 

 area, it tends to move from the place of breeding and may cover 

 in some cases a distance of 2.5 miles. The movement must be 

 made in response to a desire for food, because opportunities for 

 reproduction are unlimited. No doubt the specimens that find 

 food near the place of birth return to the source for reproduc- 

 tion, but those which migrate further for food find breeding 

 spots nearer the source of food supply. There is no evidence to 

 indicate that this movement of the house mosquito takes place 

 rapidly, but the facts in hand point rather to a slow dissemination. 



When dealing with a species that lives in the wilds, such as 

 the more important Anopheles (malaria-carrying kinds) the 

 movement to secure food may take on a very different character. 

 LePlrince and Orenstein^ have shown that Anopheles alhimanus 

 and others made their way for a distance of one-half a mile to a 

 village, apparently in search of food, and that they or others of 

 the same species made a return flight before morning. 



The fresh-water swamp mosquito when bred in small num- 

 bers seems to have the same movement as the house mosquito, 

 but when produced in enormous numbers, over a large area, may 

 cover long distances in its search for food. Under such circum- 



^ Loc. cit. 



