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 ago to study the eggs of a 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 

 v^atch-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 bj^ these insects. 



The following quotation from John A. Ryder in the 

 Entomological News for 1S92 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 



