PLANTS AND MOSQUITO CONTROL MATHESON 



427 



I did some work with another aquatic plant, Elodea {Phyllotria) 

 caiiadensis (pi. 7, fig. 2). For a number of years this plant 

 has grown in abundance in pools along a railway embankment. 

 The pools seemed ideal places for mosquito breeding, yet larvae were 

 rarely found. Three experimental aquaria were run under condi- 

 tions similar to those used with Gliara. The results are shown in 

 Table 5. 



Table 5. — Experiments tvith Elodea {Phyllotria) canadensis 



Date 



July 10 



July 12 



July 16 



July 18, 19. 



July 31 



Aug. 9 



Aquarium 

 1052-33 



pH 



Set up --[ 



Vigorous growth [9. 1 



+200 Culex larvae, j9.3 



various. 

 16 adults 9.3 



+200 Culex small .9.4 



No larvae, no adults 9. 3 



Aquarium 

 1052-34 



Set up 



Vigorous 



+200 Culex 



various. 

 22 adults 



larvae, 



+200 Culex small... 

 No larvae, no adults. 



pH 



Aquarium 

 1052-35 



Set up 



Vigorous. 

 do.... 



+200 Aedes vexans, 



small. 

 No larvae 



No larvae, no adults 



pH 



9. 1 

 9.3 



9.4 



9.4 

 9.4 



This table is self-explanatory. How are we going to account for 

 the high death-rate? Furthermore, these aquaria were exposed 

 practically the entire summer to the large numbers of adult mos- 

 quitoes that were constantly emerging from our other aquaria, yet 

 in not a single instance did we find an egg mass deposited on them. 

 I have no explanation to offer for the results. If the experiments 

 with oxygen can be successfully repeated with more species of mos- 

 quitoes I would surmise that the excessive amount of oxygen given 

 off in minute bubbles by this plant may oxidize the organic wastes 

 too rapidly, destroy any foods in solution or, when ingested by the 

 larvae, interfere with their digestive processes. 



The whole problem of selective mosquito breeding involves a fund- 

 amental study of aquatic environments. Water which is everywhere 

 so common and abundant, a substance essential to all life, a funda- 

 mental necessity to every life process, is one of the most puzzling 

 substances known. Though much has been attempted little funda- 

 mental knowledge of water chemistry, of the physicochemical fac- 

 tors of water, of water solutes and their exact constitution or re- 

 actions, etc., has been gained. Until we know something more fund- 

 amental about the physicochemical factors involved in the relation- 

 ship of water to life processes we can scarcely hope to make much 

 progress in interpreting the aquatic environments of living plants 

 and animals. 



LITERATURE CITED 

 At.t.attd, C. 



1922. Rapport Sl Monsieur le Directeur General des .services de Sante du 

 Maroc sur une MLssion autipulndiquo, Bull. Soc. Sci. Nat. Muroc, vol. 

 2, pp. 3-6. 



