6 LEAFLET 18 2, U. S. DEPARTMENT OF AGRICULTURE 



The bait should be placed beneath the trap in a broad, shallow pan, 

 about 4 inches less in diameter than the base of the cone and 1 inch 

 deep. 



Any substance attractive to the housefly may be used as bait. 

 Blackstrap molasses, 1 part, and water, 3 parts, make a convenient 

 and attractive bait. Milk and fruit waste may also be employed. 



The traps should be set where flies naturally congregate. This is 

 usually on the sunny side of a building (except in very hot weather), 

 and out of the wind. The bait pan should be kept well filled and should 

 be washed out occasionally. The catch is reduced when the flies 

 become piled more than a fourth of the way up the cone. At such 

 times the trap should be emptied. The live flies in the trap at the 

 time of emptying may be killed by immersing the trap in hot water 

 or by the use of a fly spray. The number of traps required depends 

 on the size of the premises and the abundance of flies; on a city lot 1 

 trap is usually sufficient, while on a farm from 3 to 10 traps may be 

 profitably operated. 



Electrocuting devices have been developed that are effective in 

 destroying flies. Although such devices cost much more than conical 

 traps, they require somewhat less attention. 



Fly sprays. — Where flies congregate in barns or around houses or 

 gain entrance to houses and public buildings in considerable numbers, 

 fly sprays may be used to advantage. Pyrethrum extract in a high- 

 grade kerosene (greaseless) applied with a good hand or electric spray 

 gun is very effective in killing houseflies. Each gallon of kerosene 

 should contain the extract of 1 pound of pyrethrum flowers testing 

 0.9 percent of pyrethrins. If the pyrethrum flowers are of a lower 

 grade, a proportionately larger quantity should be used. Out of doors 

 the flies must be struck with the spray. Indoors the spray should be 

 atomized into the air until there is a good floating mist. The room 

 should then be closed for half an hour, to secure the best results. 

 Many of the commercial fly sprays now on the market are essentially 

 of this composition. Pyrethrum concentrates may also be purchased 

 and appropriately diluted with refined kerosene. These are usually 

 designated as 1 to 5, 1 to 20, and 1 to 40, that is, 1 gallon of the con- 

 centrate contains the extract of 5, 20, or 40 pounds of pyrethrum. 



Flypaper, fly poisons, and fly swatters. — Flypapers, fly poisons, and 

 swatters are useful in destroying occasional flies that gain entrance 

 to homes or food-handling establishments. The safest and most 

 effective poison consists of 3 teaspoonfuls of commercial formalin to 

 1 pint of milk or water with a little brown sugar added. A convenient 

 way of exposing this is to partly fill a drinking glass with the solu- 

 tion. A small plate or saucer is then lined with a piece of blotting 

 paper and placed on the glass, bottom up. The whole is then inverted, 

 and a piece of matchstick inserted under the edge of the glass. 



U. S. GOVERNMENT PRINTING OFFICE: 1939 



