SOME ANNOYING PESTS OF MAN 345 



disappear. Smudges are located in the fields, to protect 

 the working teams, and in towns fires are kept before the 

 doors of livery barns. 



The destruction of the larvae of black-flies in streams 

 may be accomplished by pouring phinotas oil into the 

 water, by damming the smaller streams, and by sweeping 

 the larvse from the rocks in swift shallow streams. Phino- 

 tas oil was first used by Conradi in the streams of northern 

 New Hampshire. The wasteway of a dam was found to 

 contain great numbers of the larvse, covering a space 

 approximately 5 feet wide by 20 feet long. One-half of a 

 gallon of phinotas oil was poured into the water, with the 

 effect of killing all of the larvse and abating the nuisance 

 of flies at the near-by summer hotel. In later experiments 

 directed by Sanderson, a net was stretched across a small 

 stream and the water oiled for a distance of 100 yards 

 above the net. The fish descended the stream ahead of 

 the oil and were caught by the net, where they were held 

 until the oil had passed on. Many of the fish were over- 

 come by the oil at first, but within 15 to 20 minutes the 

 water cleared up and all of them revived without any 

 apparent ill effects. In a subsequent experiment where no 

 net was used the fish were subjected to the effect of the oil 

 so long that many of them were killed. In every case the 

 larvse of the black-flies were destroyed. The objection 

 to the use of this oil is its effect upon fish. It would prob- 

 ably not be safe to use it in streams flowing into pri- 

 vate ponds or lakes stocked with fish, at least not in the 

 part of the streams close to the ponds or lakes. 



When the larvse are found in restricted areas in small 

 shallow streams, it is often possible to dam the water, 

 thus increasing its depth and drowning the larvse. We 



