THE COMMON HOUSE-FLY. 151 
liquid food is sometimes the cause of diseases. Bad ulcers, 
caused by contagious diseases, are visited by flies whenever 
they have an opportunity to do so. Being hairy insects, 
and having upon their feet sucking-pads, bacteria found in 
such sores must adhere, and, if another person is visited in 
turn, disease-spores will be carried to his skin, and should 
conditions be favorable the germ of the disease thus brought 
there will not be slow to act. I had an opportunity some 
years agotostudy theeggs ofa tape-worm. These eggs were 
counted and covered with a watch-glass. A piece of freshly- 
cut beef was put in another part of the same room, the 
watch-glass was removed to give the house-flies access to 
the eggs, some of which, soon afterward, were detected 
upon the flesh, showing that even larger objects than bac- 
teria can be carried about by these insects. 
The following quotation from Joha A. Ryder in the 
Entomological News for 1892 will no doubt be of interest: 
“Cholera and flies.—It may not be amiss to call the at- 
tention of the public to the great danger from house-flies as 
agents in spreading the contagion should there be an epi- 
demic of cholera. I have repeatedly observed that these in- 
sects will ride for a number of miles on street cars, and 
doubtless also upon other vehicles of transit, such as rail- 
way coaches, etc., though I have never made observations 
upon any conveyances but the ordinary tram or horse car. 
Suppose a case: imagine a cholera victim upon the street or 
anywhere else vomiting; the flies present are attracted and 
drink until sated, and have their feet and mouth parts 
wetted with the vomit containing the germs. They then, 
perhaps, fly out into the street, take a place on a horse car, 
ride several miles, dismount, fly into another house, where 
the family are at dinner, and contaminate the food set be- 
fore them with the germs of the cholera carried on the 
mouth parts and feet of the insects. Some of the family 
sicken and die, yet no one of them will ever, perhaps, suspect 
that the flies have carried the germs, as supposed above, for 
miles from some other case. The safeguards are to at once 
clear away, disinfect with corrosive sublimate solution and 
scald the spots where the vomit has been thrown, and to be 
