The House-fly as a Carrier of Disease 157 



The use of sticky fly paper to catch the pests that gain entrance 

 to the house is preferable to the various poisons often used. Of the 

 latter, formalin (40 per cent formaldehyde) in the proportion of two 

 tablespoonfuls to a pint of water is very efficient, if all other liquids 

 are removed or covered, so that the flies must depend on the formalin 

 for drink. The mixture is said to be made more attractive by the 

 addition of sugar or milk, though we have found the plain solution 

 wholly satisfactory, under proper conditions. It should be em- 

 phasized that this formalin mixture is not perfectly harmless, as so 

 often stated. There are on record cases of severe and even fatal 

 poisoning from the accidental drinking of solutions. 



When flies are very abundant in a room they can be most readily 

 gotten rid of by fumigation with sulphur, or by the use of pure 

 pyrethrum powder either burned or puffed into the air. Herrick 

 (1913) recommends the following method: "At night all the doors 

 and windows of the kitchen should be closed; fresh powder should 

 be sprinkled over the stove, on the window ledges, tables, and in the 

 air. In the morning flies will be found lying around dead or stupified. 

 They may then be swept up and burned." This method has proved 

 very efficaceous in some of the large dining halls in Ithaca. 



The writers have had little success in fumigating with the vapors 

 of carbolic acid, or carbolic acid and gum camphor, although these 

 methods will aid in driving flies from a darkened room. 



All of these methods are but makeshifts. As Howard has so well 

 put it, "the truest and simplest way of attacking the fly problem 

 is to prevent them from breeding, by the treatment or abolition of 

 all places in which they can breed. To permit them to breed un- 

 disturbed and in countless numbers, and to devote all ovu energy to 

 the problem of keeping them out of our dwellings, or to destroy them 

 after they have once entered in spite of all obstacles, seems the 

 wrong way to go about it." 



We have already seen that Musca domestica breeds in almost any 

 fermenting organic material. While it prefers horse manure, it 

 breeds also in human feces, cow dung and that of other animals, 

 and in refuse of many kinds. To efficiently combat the insect, 

 these breeding places must be removed or must be treated in some 

 such way as to render them imsuitable for the development of the 

 larvffi. Under some conditions individual work may prove effective, 

 but to be truly efficient there must be extensive and thorough co- 

 operative efforts. 



