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MOSQUITO ERADICATION 



/ 



The aquatic plant, Naias flexilis, which is common in many 

 ponds and lakes, forming a thick growth over the bottom, nor- 

 mally does not afford protection, as it does not reach the surface 

 of the water. During severe droughts, however, it sometimes 

 reaches the surface, forming a dense mass, and, in such cases, it 

 makes excellent protection for larvae and pupae. 



he duck-weed, Spirodela polyrrhiza, sometimes forms an 

 almost continuous cover over a pond or a portion of it, but 

 observations indicate that larvae are rarely, if ever, found 

 therein. It is considered likely that the covering is so dense that 

 breeding cannot take place. 



Fig. 134. — Picture showing how water-lilies furnish protection for mosquito 

 larvae. Note the water in the leaves with turncd-up edges, and how completely 

 the larvae therein are protected from fish. 



The smart-weed, Polygonum, is another plant that usually does 

 not afford protection, and which may sometimes be obnoxious 

 to mosquito larvae, according to Hildebrand, 1 who says: "Many 

 places overgrown with this weed were repeatedly examined, but 

 mosquito larvae were not found, even in apparently favorable 

 hiding-places." 



ELIMINATING LARVA-PROTECTING PLANTS 



It is evident from the study of plants in relation to fish control 

 that to get full results, it is necessary to remove from the pond 

 lake, stream or other natural breeding-place algae and other 



1 "Fishes in Relation to Mosquito Control in Ponds," U. S. Bureau of 

 Fisheries, 1919. 



