194 The Control of Mosquitoes 



debris, which afford better protection to mosquito 

 larvae than is given by standing trees. When 

 trees are not standing close together, unless their 

 branches reach the water surface, collections of 

 debris are not apt to gather and remain near them. 

 In the absence of an oil film small fish devour 

 most of the larvae close to the tree trunk. After 

 the tree decays and falls, its twigs and branches 

 may tend to collect floating debris and afford 

 protection to larvae. In the tropics vines and 

 plants may grow on floating logs and become the 

 nucleus of floating islands. 



