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 
muscce domestica? 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 
