PREVENTIVE MEASURES 187 



cent, solution and should be diluted with water down 

 to five per cent, or eight per cent. ; in other words, add 

 five to six times as much water. This solution, he 

 says, should be sweetened with sugar or made attractive 

 by adding milk. 



He advises partly filling a shallow vessel, such as an 

 individual butter dish, and placing it upon the table 

 or in the show window. He states that the flies drink 

 this material and die not far from the containers. In 

 the dining-room where there is water, milk, or other 

 liquid food, flies are said not to be so greatly at- 

 tracted to the formalin, but where this is made the 

 only source of drink for the insects the results are 

 said to be remarkable. Herms recommends that all 

 other liquids except the formaldehyd dishes in a 

 given room should be removed or securely covered 

 in the evening, so that the flies have only the formal- 

 dehyd to drink early in the morning when they begin 

 to fly. 



Some careful experiments were tried during early 

 February, 1911, at New Orleans, La., at the request 

 of the writer, by Mr. T. C. Barber. Mr. Barber's notes 

 indicate success. The mixture used was formaldehyd 

 ( forty-five per cent. ) , two ounces ; sugar, two ounces ; 

 water, ten ounces. On February 14th he placed some 

 of this solution in an open saucer in the show window 

 of a grocery store, where a few flies were present. 

 After being left about one hour, seven dead flies were 

 found in the window, which had previously been thor- 

 oughly cleaned. He then placed the material in two 



