FLIES FOUND IN HOUSES 4 1 



the Ptilicidie (fleas) which are the real culprits, and consequently 

 it is a benefactor instead of being injurious" (Verrall, 1909, 

 p. 600). 



From its habits it is very unlikely that this fl\' transmits 

 disease. 



The larva; of all the species mentioned except P. rudis and 

 6", fenestralis feed on animal and human excreta, carrion and 

 decaying vegetable matter, and the flies frequent these substances, 

 and consequently carry putrefactive and faecal bacteria both in 

 and on their bodies. 



Further information on the relation of the sexes to the 

 materials mentioned is given in Chapter vii, and a list of the 

 species which breed in or frequent human excrement in 

 Chapter XXVI. 



CHAPTER III 



LIFE-HISTORY OF THE HOUSE-FLY {M. DOMESTICA) 



The description of the life-history of the house-fly given in 

 this chapter is mainly taken from Newstead's (1907) account of 

 his very careful study of the subject in the city of Liverpool. 



" The eggs are laid in small irregular clusters, or in large 

 collective masses consisting of many thousands of individual 

 eggs. They are almost invariably on or in such substances as 

 will provide food for the larvae or maggots. They are usually 

 placed in narrow crevices near the surface, but, occasionally, also 

 at a distance of four to six inches below the surface, \h<t favourite 

 spots in all cases being fermenting vegetable matter or the 

 refuse lying immediately over such materials, or in refuse that is 

 likely to ferment. They are often laid, however, on materials 

 which do not ferment, and in all such cases (in this country at 

 least) the developmental cycle is greatly prolonged." 



" The eggs are pure white, and present a highly polished 



