1^6 EXPERIMENTS IN DESTROYING BLACK-FLIES 



J 



breeding-grounds a simple means of destroying the pests. He 

 also found that in a brook three feet wide where in June the 

 flies were breeding in vast quantities, and in which he had 

 poured one gallon of Phinotas oil, the young stages of the flies 

 had been killed off for a distance of one eighth of a mile from 

 the place of application. As regards fish he found that they 

 swam rapidly down stream as soon as it was applied, and ap- 

 parently were able to escape with no evil results to themselves. 



Shortly after the treatment the adult black-flies became so 

 scarce that the hotel manager discarded the smudges which for 

 the past twelve summers had been in daily use for the protec- 

 tion of the guests. 



The Phinotas Chemical company, New York city, furnished 

 in the spring of 1904 two grades of oil for experimental use. 

 One is called soluble oil, and the other is the insoluble oil used 

 last year. On mixing with water the differences between the 

 two are readily seen. The former mixes at once, while the 

 latter sinks to the bottom and gradually rises. I tried both 

 sorts in the water at the outlet to the college reservoir where 

 the black-fly larvas were abundant. Both appeared to be 

 effective in killing them, but further experiments are necessary 

 to determine which is the better. Very likely under some 

 conditions one may be better, and under others, the other. It 

 is probable that the insoluble oil would be less likely to injure 

 fishes. 



It is unlawful in this state to kill fish by the use of any 

 poisonous substance. Consequently care must be taken in the 

 use of oil against black-fly larvae. An amendment to the law 

 by which town authorities might exterminate the black-flies 

 on their breeding-grounds is desirable. There need be little if 

 any injury to fish, through an intelligent use of the oil remedy. 

 With the sweeping method there is no danger whatever. 



The common species of black-fly in New Hampshire as de- 

 termined through the courtesy of Dr. L. O. Howard of the 

 United States department of agriculture is Simulium venus£wm 

 Say. 



I believe that these experiments justify the hope that in the 

 near future the black-fly will be more easily controlled in cen- 

 tres of permanent or temporary population than is the mosquito. 



