418 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



after daylight. The dead flies, swept up about eight a. m., measured 

 about one pint, representing fully 5,000 flies. 



This experiment was repeated for three successive days and about 

 one pint of dead flies were swept up every morning. In addition to 

 the flies actually secured many dropped dead outside the ^vindows. 



My next experiment was to use a mixture of half milk and half 

 water instead of whole milk. Formalin was added in the same pro- 

 portion, one ounce to sixteen ounces of diluted milk. This proved 

 to attract the flies as well as whole milk. 



Several variations in the proportion of formalin and milk were 

 tested, but my conclusion is that the use of one ounce to sixteen is 

 most effective. The following method of stating the formula has 

 been used for newspaper articles, in order that every housekeeper 

 can prepare it easily: 



"One ounce (two tablespoonfuls) of 40 per cent formalin; sixteen 

 ounces (one pint) of equal parts milk and water. 



"This mixture should be exposed in shallow plates and by putting 

 a piece of bread in the middle of the plate, it furnishes more space for 

 the flies to alight and feed and in that way serves to attract a greater 

 number of them. Whole milk can be used, but the diluted milk 

 seems to be just as successful. The formalin can be purchased for 

 fifty cents a pint." 



A very conclusive test of the efficiency of the above formalin mixture 

 was made in a large calf barn where flies were extremely numerous. 

 Six plates of the mixture were placed in the passage way between 

 the stalls. This passage way is about six feet wide and thirty feet long. 

 The poison mixture was exposed at 12 o'clock, noon, and left until 

 8 o'clock the next morning. The dead flies when swept up measured 

 three quarts, and certainly one half as many died in the stalls on 

 each side. I estimated that we killed between forty and fifty thousand 

 flies in twenty hours by this experiment. 



At the writer's suggestion many housekeepers in Raleigh and West 

 Raleigh have used the formalin as recommended above, and several 

 have reported the killing of flies by the pint and quart. A gentleman 

 in charge of a farm where a large horse barn is maintained tells me 

 that he poisoned a gallon of flies the first day he tried the mixture. 

 This statement was vouched for by other witnesses in whom I have 

 perfect confidence. 



A good place to expose the formalin mixture is on the front and 

 back porches, where flies are frequently numerous, and waiting to 

 enter when the doors are opened. I know of several people who have 

 used it successfully in this manner. 



The use of the formalin-milk mixture in dwelling houses has not 



