188 MOSQUITO ERADICATION 



"It is very interesting to observe how quickly the top minnows learn 

 to follow the workmen engaged in cutting and raking vegetation from 

 ponds. They soon become quite tame, and schools of them work 

 almost under the tools of the laborers, catching mosquito larvae and 

 other insects as quickly as their hiding-places are destroyed." 



All aquatic plants, however, do not furnish protection for 

 mosquito larvae and pupae against fish, and some even may be 

 positively repellent to them. Grasses and rushes and other 

 plants having straight stalks and no submerged leaves afford no 

 protection. Areas overgrown with plants of this nature have 

 been repeatedly examined for breeding, but, if the water was 

 stocked with mosquito-destroying fish, no larvae were found. 

 Plants which are likely to hang over into the water after maturity 

 or after freshets, etc., should be removed. 



PLANTS IN RELATION TO FISH CONTROL 



The following plants appear to provide good protection, and 

 may cause considerable trouble, according to Hildebrand: 1 the 

 aquatic grass, Hydrochloa carolinensis; "coon-tail moss," a 

 species of Myriophyllum; and algae. Continuing, Hildebrand 1 

 says: 



"The aquatic grass grows in shallow water and along the shores. It 

 has many slightly submerged leaves, over which the horizontally 

 floating or swimming Anopheles larvae hover, out of sight and out of 

 reach of the fish. Wherever this plant occurs, some Anopheles larvae 

 are almost sure to be present regardless of the abundance of Gambusia. 

 It, therefore, is obvious that, if this plant occurs in ponds in which 

 mosquito control is desired, it must be removed. This may be done 

 by cutting and raking it or, if growing in soft mud, it may be pulled up 

 by the roots. 



"The plant locally (at Augusta, Ga.) known as 'coon-tail moss' 

 causes trouble only when it becomes detached and rises to the sur- 

 face. . . . This floating mass must be removed from time to time; 

 this can best be done on a windy day, when it drifts inshore. 



"Algae often form mats which float at or near the surface. Mos- 

 quito larvae, particularly Anopheles, find protection from fish over and in 

 these mats. Copper sulphate was used in the proportion of 8 pounds 

 to 100,000 gallons of water for killing the algae, but this treatment 

 must be repeated frequently. . . . Oil, if used in moderate quantities, 

 is not injurious to fish; it can be quickly and conveniently applied and it 



V'Fishes~in"Relation to Mosquito Control in Ponds," U. S. Bureau of 

 Fisheries,* 1919. 



