70 THE HOUSE FLY— DISEASE CARRIER 



Mr. H. T. Giissow, Dominion Botanist of Canada, 

 quoted by Hewitt, the fungi reared in this way have 

 numbered seven species, while the bacteria have num- 

 bered eleven species. 



Protozoan Enemies of the House Fly 



Certain microscopic protozoa of the group Flagel- 

 lata have been found in the alimentary canals of vari- 

 ous insects, and one species known as Herpetomonas 

 miiSccB domesticcB has been found in the intestine of 

 the house fly. The genus to which it belongs is said 

 by Calkins to be the most primitive and least changed 

 from the free-living forms of the flagellated intestinal 

 parasites. It is a general parasite of flies of very wide 

 distribution. It was carefully studied by Prowazek in 

 1904 and by Captain W. S. Patton of the Indian Med- 

 ical Service in 1908 and 1909. 



Patton found that in Madras, India, about one hun- 

 dred per cent, of the flies caught in the bazaar meat 

 shops are infected with this parasite, and he made an 

 exhaustive study of its life history which continued 

 for more than a year. He found that it exists in three 

 stages which he calls the preflagellate, the flagellate 

 and the postflagellate. The first stage is usually found 

 in the midgut, the parasites lying in masses within the 

 peritracheal membrane. They are round or slightly 

 oval bodies of very minute size, which multiply by 

 simple longitudinal division or by multiple segmenta- 

 tion so that a large number is formed in a short time. 

 The flagellate stage is characterized by the projection 



