18 MOSQUITO ERADICATION 



conditions are favorable — that is, if the weather is warm, the 

 water rich in food and other factors are right — the egg may 

 develop into an adult mosquito in 8 to 10 days. 



The length of life of the adult mosquito varies with conditions. 

 The average mosquito probably lives several months under 

 favorable circumstances. Guiteras kept one alive in Havana for 

 154 days, and it is frequent to keep them alive in laboratories for 

 70 to 90 days. Without water, however, the mosquito will 

 perish in 4 or 5 days. 



The character of the breeding-place varies with the species and 

 with conditions. Thus, the domestic mosquitoes generally 

 choose water impounded in artificial containers about homes, 

 such as barrels and cisterns, tin cans and bottles, cesspools, 

 shallow wells, etc. The fresh-water sylvan mosquitoes may be 

 found occasionally in this class of breeding-place, as well as in 

 forest pools, swamps, ponds and streams, their usual breeding- 

 places. The character of breeding-place of any given group 

 may be modified by conditions. 



VARIATIONS IN EGGS, LARVAE AND PUPAE 



The eggs, too, vary materially with the different species. The 

 eggs of the Culex are deposited vertically in large, brownish 

 rafts; those of the Aedes and Anopheles, on the other hand, are 

 found isolated, one by one, on their sides. 



The habits and appearance of the larvae also present noticeable 

 differences. Although all larvae are aquatic animals, they are, 

 nevertheless, nearly all air breathers, lying just under the sur- 

 face of the water and connecting with the air supply from time 

 to time by means of a breathing siphon. The Anopheles larvae 

 recline under the surface of the water in a horizontal position, 

 while the Culex, Aedes and others, on the contrary, hang with 

 their heads down. 



The pupae of all species do not eat, having no mouth. Like 

 the larvae, however, they are air breathers, breathing through a 

 pair of trumpet-shaped tubes which are connected with the thorax. 



Some species pass the winter as adults hidden in natural 

 shelters; others as larvae; and still others as eggs. The eggs 

 of some mosquitoes will retain their vitality after having been 

 perfectly dry for months; exposure to water for a few hours will 

 result in the hatching of larvae. These varied methods of 

 survival render extinction of the race impossible. 



