JOURNAL 



OF 



ECONOMIC ENTOMOLOGY 



OFFICIAL ORGAN AMERICAN ASSOCIATION OF ECONOMIC ENTOMOLOGISTS 



Vol. 4 OCTOBER, 1911 No. 5 



FORMALIN FOR POISONING HOUSE FLIES PROVES VERY 

 ATTRACTIVE WHEN USED WITH SWEET MILK 



By R. I. Smith, North Carolina Experiment Station 



During the early part of June, 1911, while attempting to reduce 

 the flies at the horse barns and dairy of the North Carolina Agricultural 

 and Mechanical College, I attempted to poison them with formalin, 

 and secured rather remarkable results. House flies (Musca domes- 

 tica) were very numerous when the work was commenced, owing to 

 the fact that the manure had been allowed to accumulate for six or 

 eight weeks. In the milk room (which was screened shortly after- 

 ward) the flies covered the walls and ceiling, and the straining cloth 

 at milking time was actually black with flies. In justice to the College 

 and the writer, allow me to explain that this cUsgraceful condition 

 was soon remedied and that during the past three months the dairy 

 has been remarkably free from flies. 



My previous experience with formalin for poisoning flies had been 

 confined to using it a few times in the laboratory in the proportion 

 of one part to twenty parts of sweetened water, but realizing that the 

 poison must be made attractive if used successfully in the milk room 

 of a dairy, I decided to try it with milk instead of water. 



My first experiment i)roved successful. This was the addition of 

 one ounce of 40 per cent formalin to sixteen ounces of fresh milk. 

 This mixture was placed in four shaflow tin plates and set on the 

 floor of the milk room about 3 o'clock one afternoon. The flies 

 commenced to feed and die within a few minutes, and continued to 

 die rapidly even while the evening's milk was being brought in and 

 strained. These plates of poison were left over night and the milkers 

 advised me that the flies were feeding greedily the next morning soon 



