EXPERIMENTS IN DESTROYING BLACK-FLIES I35 



come continuously. A large part of the encompassed area is 

 taken up by a beautiful lake. 



Upon his arrival Mr. Conradi made a careful survey of the 

 entire locality, finding no flies breeding in the swiftly-running 

 shaded streams along the mountain sides, but finding vast 

 numbers breeding in the shallow, sunlit waters at the waste- 

 way from the lake and in two or three other places. His notes 

 upon the first experiment with the oil treatment are as follows : 



" At the wasteway near the lake dam where the stream is 

 approximately five feet wide, one third of a gallon of Phinotas 

 oil was applied at 4 a. m., June 22. The effect was at 

 once noticeable. At 2 p. m. the same day, most of the larvae 

 were dead, while the remainder were sluggish. On the after- 

 noon of the next day, the conditions were carefully investi- 

 gated, and all the larvae were found to be dead, not only 

 where the oil was applied but for ten feet or so ahead as well. 



"The oil was applied by 

 simply pouring it over a 

 shingle, thus scattering it 

 somewhat. It sinks and 

 rises and lingers long about 

 the place. Stones in the 

 water picked up forty-eight hours after the application had a 

 thin film of oil still on them." 



When Mr. Conradi reported the results of his trip, it 

 seemed to me that the problem was in part at least solved, the 

 chief perplexing feature being the possible deleterious effect 

 upon fish of the application of the oil in quantity. From the 

 similarity of the breeding-places he found to the one I had 

 been observing, it occurred to me that a little work with stiff' 

 brooms in sweeping free the masses of larvae, and then catch- 

 ing them down stream on wire netting stretched in the water 

 might be helpful where the oil could not be applied. Accord- 

 ingly, I sent to Dixville Notch a barrel of Phinotas oil and a 

 supply of stiff stable brooms. When these arrived, Mr. Con- 

 radi went again with specific directions as to the use of the 

 brooms and the application of the oil, especially, in the latter 

 case, as to the effect upon fish life. He found that the sweep- 

 ing method was entirely practicable and offered in some 



Pupa of Black-fly. Magnified. 



