Vol. XXI, No. 5 



WASHINGTON 



May, 1910 



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MATHONAIL 

 ©(SHAIPIHIIKD 

 A(SAM] 



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THE HOUSE-FLY 



By N. a. Cobb 



IVith photographs made specially for the Natio)ial Geographic Magazine 



bv N. A. Cobb 



THE fly referred to in these pages 

 is the one most commonly found 

 in our houses — the Miisca doiiies- 

 tica of Linnaeus. At most seasons nine 

 flies out of ten found in houses are of 

 this kind. In some of the paragraphs, 

 however, the statements are inferences 

 fully justified by experiments with very 

 .similar species. 



Speaking broadly, man has made the 

 house-fly ; it has developed along with 

 the human dwelling. If we had no 

 closed-in dwelling places it is doubtful if 

 the house-fly as at present constituted 

 could continue to exist. It thrives sim- 

 ply because we afford it food, protection, 

 and breeding places. 



It is a comforting thought that just as 

 we have made the house-fly, so we can 

 unmake it, but it is discouraging to think 

 how long it will take us at the present 

 rate. 



Following man into all but the coldest 

 climates, this fly is found in nearly all 

 parts of the world, and its name in many 

 languages denotes the fact that it is an 

 indoor or household insect. In the past 

 it has been looked upon with indiffer- 

 ence, or, at most, struck at with objur- 

 eation when too familiar. It figures in 



fable and poetry, not without some de- 

 gree of praise occasionally. Its reputa- 

 tion as a harmless, innocent, lively, and 

 interesting creature will die hard. 



In reality it is one of our worst ene- 

 mies. Its relations to human health and 

 sanitation are most important, and yet 

 for years all efforts to bring the facts 

 properly to the attention of municipal 

 authorities met with indifference or ridi- 

 cule. We had become so accustomed to 

 put up with the losses of life and prop- 

 erty directly traceable to files that we 

 no longer had the capacity to grasp the 

 significance of very simple facts — facts 

 demonstrable by almost any one at the 

 expense of a few minutes, or at most a 

 few hours, of observation or experiment. 

 x\gain, it was so easy to turn the whole 

 matter into what passed for a j^ke that 

 the gravity of the subject was lost 

 sight of. 



Latterly, however, a gratifying change 

 is taking place in public opinion, due no 

 doubt to what has been discovered ab(nit 

 mosquitoes. It has been shown that 

 these latter insects are one of the main 

 factors in the production of diseases that 

 frequentlv have claimed their victims bv 

 hundreds, or even thousands, under most 



