FISH CONTROL 



1S9 



is very effective, for the algal pads act like sponges, retaining the oil and 

 making them uninhabitable for the mosquito. 



"Water lilies do not, as a rule, appear to furnish much protection 

 while growing, but some of the plants die from time to time. The leaf 

 then partly sinks, forming a depression over the center, while the edges 



Fig. 1 



furnishes 

 Service.) 



32. — Showing growth of aquatic grass in corner of pond. Sue 

 excellent protection for mosquito larvae. (After U. S. Public 



h grass 

 Health 



(U. S. Public Health Service) 

 Fig. 133. — Treating pond with copper sulphate to kill algae. Laborer is 

 dragging a small bag of the chemical through the water by means of a pole. 



remain at the surface. The cup thus formed holds enough water to 

 support mosquito larvae, and with respect to fish the larvae contained 

 therein are perfectly safe. When the dead leaves drift inshore they, of 

 course, frequently make places inaccessible to fish." 



