FLY CONTROL. 59 
a large bin with a perforated bottom through which the maggots 
can find their way. Beneath the bin must be a pan or basin of 
metal or concrete, either containing an inch or more of a weak 
disinfectant or water, covered with oil, which will kill the maggots 
when they drop in. Such a basin should have straight, vertical 
sides, and if connected with a sewer, could be easily flushed out 
once a week. Much remains to be done to perfect such a trap 
for practical use. 
We have had frequent requests from people wishing to know 
what they could use in order to clear a house of flies, after they 
have screened the doors and windows. Many substances have 
been recommended and it was difficult to know which was the 
best to advise. With this in view, several tests were made of 
these fumigants during the past summer. Fumigation with hydro- 
cyanic acid gas would, of course, kill flies, but owing to the danger 
which might result from its use by an incautious person, it seems 
advisable not to suggest it. The cost is also prohibitive to most 
people. We tried the following, which are easily manipulated 
and the ingredients of which are easily secured: phenol-camphor, 
formaldehyde-gas, cresol, carbolic acid, sulphur, chlorine gas, and 
pyrethrum (insect powder). Only three of these gave satisfactory 
results. 
Formaldehyde was used at the rate of one pound of 40 per 
cent formaldehyde with eight ounces of potassium permanganate, 
to each 1,000 cubic feet of space. When the room was left closed 
for four hours, it destroyed practically all of the flies. Out of 
nearly 2,300 flies, only twelve survived. Formaldehyde and potas- 
sium permanganate can be purchased at any drug store. The 
permanganate should be spread evenly over the bottom of a large 
enameled pan and the formaldehyde poured over it. Formalde- 
hvde gas is liberated as a result of the chemical action which takes 
place. Where this gas is used for disinfection purposes, a con- 
siderable quantity of water is added to the formaldehyde before 
pouring it over the permanganate. A parallel experiment, how- 
ever, in which water was used with the formaldehyde did not give 
us as good results, fully 10 per cent of the flies surviving. Before 
fumigating, the room or rooms must be made as nearly air-tight 
as possible by closing up all openings, plugging up cracks in 
walls and around windows, etc. After fumigating, the room must 
be aired out for a couple of hours before entering. An individual 
will, however, not be apt to enter a room full of formaldehyde gas, 
