U. S. B. F.—Dos. 874. PLATE Vi. 

FIG. 16.—DISTANT VIEW OF POND. MUCH MARGINAL VEGETATION WHICH 
USUALLY FURNISHES SOME PROTECTION FOR MOSQUITO LARVA. 

FIG. 17.—SHOWING MARGINAL VEGETATION REMOVED. 

FIG. 18.—SPRAYING OIL ON ALGAL PADS, 
In foreground is seen some of the aquatic grass, Hydrochloa carolinensis, which 
provides excellent protection for mosquito larvae. 
