12 



AN EXPERIMENT AGAINST MOSaUITOES.* 



By L, O. Howard. 



Oue of the most reasonable of the recommendations Trhich have been 

 made from time to time, and which look toward the reduction of the 

 mosquito plague during the summer months, is the application of kero- 

 sene to restricted and Ashless breeding ponds. Although this remedy 

 has often been suggested, I know of no careful records of actual ex- 

 periments, and consequently deem the following account of a recent 

 experience worthy of publication. 



On the 5th of July of the present year I noticed for the first time a 

 few mosquitoes on the porch of my cottage, in the Catskill Mountains 

 of Kew York. The elevation of this cottage is about 2,500 feet, and 

 mosquitoes have hitherto been rare visitors. The month of June, how- 

 ever, was very wet, and as I had noticed several pools of surface water 

 in the immediate vicinity, the presence of these mosquitoes caused me 

 some anxiety, as I feared they would continue to breed throughout the 

 summer and prove a serious anuoyance later in the season. One of the 

 surface pools mentioned was situated upon my own grounds, and upon 

 first noticing the mosquitoes I walked out to this spot. It was about 

 dusk, and a dozen or more female mosquitoes were found buzzing about 

 the surface of the water. I immediately sprinkled four ounces of coal 

 oil upon the surface of the pond. 



Upon the following day I carefully measured the little pool and 

 found that it contained 60 square feet. From day to day until July 15, 

 when I returned to Washington, observations were made. Severe rain- 

 storms occurred on the 8th and 10th of the month, and after the first 

 of these the pool lost the glassy iridescent surface effect given by the 

 almost continuous but infinitesimally thin layer of kerosene. Never- 

 theless the insecticidal effect of the latter did not seem to diminish, 

 although I could no longer perceive any coal-oil odor. Many dead in- 

 sects were found floating upon the surface of the water the next morn- 

 ing after the application, and these increased rapidly up to the time of 

 my departure. The pool, which upon the evening of the 5th had been 

 teeming with animal life, contained no li^dng insects during the follow- 

 ing ten days. 



The actual good accomplished is shown by the following facts : All 

 aquatic larvae, including those of the mosquito, were killed. The kero- 

 sene, curiously enough, seemed to exercise no deterrent effect upon the 

 adult female mosquitoes. They still continued to attempt to deposit 

 eggs and in this attempt were destroyed. This is, in my opinion, a 

 most important point, and one which has hardly been anticipated. 



On the tenth day after the application a careful count of the dead 



* Head before the meeting of the Association of Economic Entomologists at Eoches- 



ter, N. Y., August 16, 1892. 



