U. S. B. F.—Doc. 874. PLATE IV. 

FIG. 10.—SPRAYING OIL ON ALGAL PADS TO DESTROY THEIR USEFUL- 
NESS AS HIDING PLACES FOR THE IMMATURE MOSQUITO. 


FIG. 12.—RUSHES GROWING IN END OF POND. THESE PLANTS RARELY 
PROVIDE PROTECTION FOR MOSQUITO LARVA, 
