THE HOUSE FLY 67 



in grooves which will permit of sliding up when it is neces- 

 sary to clean the window panes. 



A solution of formalin is very effective in killing flies. 

 Formalin is sold by all chemists in a 40 per cent, solution. 

 To one part of this 40 per cent, solution add five parts 

 of water. Sweeten with sugar and colour with milk. 

 Instead of sugar and fresh milk, the sweetened form of 

 condensed milk may be added to it. Partly fill a shallow 

 dish with the mixture and place it where flies are most 

 likely to get at it. Flies will drink the mixture greedily 

 and die within a few seconds, often around the dish. 

 Formalin is an excellent substitute for poisons, for a fly 

 killed by formalin is not poisonous if accidentally swallowed 

 by man, beast, or bird, nor is the solution poisonous unless 

 swallowed freely. The dish of formalin mixture should 

 be placed out first thing in the morning, and all other 

 liquids in the room carefully covered up, as flies are hungry 

 and thirsty when they first begin to fly in the early hours 

 of the morning. This covering up of all other foods and 

 drinks is important, and should not be overlooked. 



It is advisable to use small dishes and make the mixture 

 fresh each day. Where there is danger of the mixture 

 getting upset, a piece of dry bread may be placed in the 

 dish. This will soak up the liquid, and the flies will suck 

 it from the bread. 



Flies usually roost for the night on the ceiling. Ad- 

 vantage may be taken of this fact to kill them by means 

 of fumigation. Before retiring for the night, close up the 

 room as thoroughly as possible. Heat an old shovel, 

 frying-pan, or bit of sheet iron in the fire. Sprinkle a 

 heaping teaspoonful of pyrethrum powder over it. When 



