REPORT ON MOSQUITOES. 137 



from pupa to adult, took place after the addition of the Bordeaux 

 mixture, and that the killing was irregular, hence was apparently 

 indirect. It is evident from these facts that the material, cannot 

 serve as a practical insecticide. 



The experiments just detailed bear out Mr. Dickerson's con- 

 clusions and these are not really opposed to the statements made 

 by Messrs. Moore and Kellerman in the Bulletin above cited. 

 Thc}^ state, page 16, that "Mosquito larva; die at a concentration 

 varying from ten thousand to two hundred thousand." The 

 weakest effective solution we found was one to fifty thousand, and 

 that was utterlv unreliable, while not a mature larva or pupa was 

 killed at any strength. On page 24 the authors state : "The use 

 of some such method for the destruction of mosquito larvae also 

 seems worthy of attention. The mere removal of the great mass 

 of algal growths in stagnant pools undoubtedly reduces the num- 

 ber of larvae by destroying this source of their food and depriv- 

 ing them of protection from fish and other enemies. This is 

 probably the explanation of the reported decrease in the number 

 of mosquito larvee after spraying a lily pond with Bordeaux 

 mixture, although it is possible that the strength of the solution 

 used may have been partly responsible for their death. It is be- 

 lieved that it will not be impracticable to use the amounts of cop- 

 per sulphate necessary to actually destroy such larvae. Certainly 

 this method, if effective, offers considerable advantages over any 

 now in use and should be thoroughly tested." 



It will be observed that the authors make suggestions only and 

 no direct statements of fact, and thev give what I believe to be the 

 true action of copper in the suggestion that it deprives the larvae 

 of food. It will be observed, if the chapter on the food of mos- 

 quito larvae is consulted, in comparison with the tables in the cop- 

 per Bulletin, that practically all the forms determined by Mr. 

 Parker succumb quite readily to the copper sulphate. If, then, 

 the mosquitoes depend upon this food to so large an extent that 

 they must starve without it, we can readily account for the slow 

 dying off in our experiments. The New Brunswick city water, 

 it is fair to say, is decidedly poor in quality and rich in algae. The 

 breeding water in the pails was always more or less foul and the 

 lot and gutter pools were not nice. Therefore in all the experi- 

 ments the amount of wriggler food was present in great abund- 

 ance. It is probable, also, that the copper exercised a toxic effect 

 through the stomach and that would explain why the young died 

 first. It also gives a reason for its failure to affect full fed larvae 

 and pupae. It is possible that in some areas where there are no 

 fish the copper sulphate may have a place, but at one to fifty thou- 



