U.S. B. F.—Doc. 874. PEATE iil? 
FIG. 7.—~AQUATIC GRASS GROWING ALONG THE SHALLOW EDGE OF A 
POND WHERE IT FORMS PROTECTION FOR MOSQUITO LARVA, 
FIG. 8—FLOATING PLANTS OF MYRIOPHYLLUM AND DEBRIS WHICH 
PROVIDE PROTECTION FOR MOSQUITO LARVA. 
FIG. 9—TREATING POND WITH COPPER SULPHATE FOR KILLING ALGA. 
LABORER IS DRAGGING A SMALL BAG OF THE CHEMICAL THROUGH 
THE WATER BY MEANS OF A POLE. 
