INFLUENCE OF ENVIRONMENT 263 



to cling to shelter. Winds of low velocity (ten miles or less per hour), 

 of high temperature (80°F.) and high humidity appear to be the ones 

 that favor long flights. 



The observations of practically all investigators indicate that the 

 salt marsh species in long migrations travel with the wind. On the other 

 hand, LePrince and Orenstein (17) found Anopheles flying against the 

 wind or at right angles to it. Russell, however, records An. annulipalpis 

 as coming aboard ship on a breeze from land. The investigations of the 

 author and later of Clarke show that the movements of A. vexans do not 

 follow prevailing winds. 



The available facts on adult mosquito movements indicate the neces- 

 sity of knowing the composition of the mosquito fauna throughout the 

 territory to be given protection so well and so thoroughly that adequate 

 measures may be taken to eliminate invasions from outside the bound- 

 aries. 



