98 



of water. At this rate 1 ounce of the permanganate would make 

 120 pints or 15 gallons uninhabitable for mosquito larvae, at a cost of 

 li cents for material. 



Under this name a preparation, mostly permanganate of potash, 

 was placed upon the market. It was advertised to some extent, and 

 claims were made which, if they were only approximately true, would 

 solve the mosquito question at once and for all time. A small pinch 

 was supposed to rid an ordinary lawn of all insects, and 5 pounds would 

 keep an acre clear for an entire season. So on August 9 a small lot of 

 larvae and pupae was placed in four 1-ounce bottles. As the " pinch" 

 was the measure provided for in the directions for use, I put " pinches" 

 of varying quantity into the bottles. The resulting color ranged from 

 a rather clear red to a deep opaque purple. August 10 the deepest- 

 colored liquid was so diluted as to make things visible, and it was 

 found that, while all the larvae were dead, all the pupa? were alive and 

 active. 



A second bottle, in which the liquid was just transparent enough to 

 see through, had a few pupae and quite a number of full-grown larvae 

 when the experiment began. August 10 the hood over the bottle 

 was full of adults and most of the larvae had changed to pupae. Only 

 a few larvae remained, but these were very lively. August 11 adults 

 from the last batch of pupa? began to make their appearance and the 

 experiment was closed. 



In the other bottles the larvae developed well, and apparently paid 

 no attention to the presence of the permanganate. 



Practically these permanganate of potash preparations are of no 

 value, and this conclusion agrees with that reached by Dr. L. O. 

 Howard. 



SALT. 



Culex pungens has not been normally found in salt or even brackish 

 water, and I do not believe that the female ever forms its egg boats on 

 such waters. It became a matter of some interest, therefore, to deter- 

 mine what effect the addition of salt would have, and I transferred the 

 contents of one of my garden pails to a 2-quart jar half filled with 

 water. The range was from egg boats to pupae, and after twenty- 

 four hours the water was one mass of wrigglers, most of them small 

 or very small. I added a small handful of common salt, dropping it 

 through the meshes of the bobbin et hood until it formed a layer at 

 the bottom, which dissolved completely in an hour or two. Forty- 

 eight hours afterwards no bad effects were observed, and the larvae 

 appeared to enjoy the salt water immensely. I doubled the amount of 

 salt previously used, and it formed a layer over the entire bottom of 

 the jar and did not completely dissolve for ten hours. Twenty-four 





