38 THE POPULAR SCIENCE MONTHLY 



The house fly does not bite, but its mouth parts are fitted for lap- 

 ping and sucking up liquids. Another fly (Stomoxys calcitrans), 

 called the stable fly, pierces the skin, and as this fly resembles the 

 house fly and sometimes enters houses, many persons are mistaken in 

 thinking that the house fly actually bites. 



Breeding in filth and visiting all sorts of foul waste and decaying 

 animal aud vegetable matter and crawling over it, flies can not help 

 becoming contaminated. At the first opportunity they will also crawl 

 over food in the kitchen and drink from the milk pitcher. In this way 

 some of the germs are rubbed off and adhere to the food and are swal- 

 lowed with it by human beings. The diseases most commonly dissemi- 

 nated in this manner are those of the alimentary canal known as enteric 

 diseases, such as typhoid fever, cholera and dysentery, the germs of 

 which are voided in fecal matter, which if left exposed is certain to be 

 visited by hundreds of flies, and some of the causative bacterial germs 

 of these diseases are thus transferred to food, and infection is thus 

 made possible. But it is not these diseases alone that may be and are 

 occasionally carried by flies. There is considerable evidence to show 

 that the house fly and its near relatives may carry the anthrax bacillus 

 an their digestive systems and deposit the germs with their excretions, 

 •or may carry these germs exteriorly if the flies have visited foul matter 

 "containing them. They may then infect persons by crawling over 

 wounds or even food. Flies may carry the germs of tuberculosis by 

 "visiting sputum and then crawling over the mouth and nose and' food 

 of persons. Kuttall made some interesting experiments in 1897 which 

 proved that house flies not only may carry the germs of bubonic plague, 

 commonly carried by fleas, but that they may actually die of the 

 disease. 5 



It has been shown that the causative germs of some of these diseases 

 may be and are taken into the digestive tract of the house fly and de- 

 posited upon food, confections or other substances. Thus the tiny fly 

 specks which are the bane of every good housekeeper may be positively 

 dangerous. 



Formerly it was supposed that the house fly bred only in manure 

 from the stables, and that it did breed in such places was pointed out 

 as early as 1831 by Bouche. In 1873 Packard, and in 1880 Taschen- 

 berg, published accounts of the house fly showing that it usually breeds 

 in horse manure. Packard records fourteen days as the period re- 

 quired to develop a generation. Dr. Howard in 1895 6 studied the in- 

 sect, and had some difficulty in rearing it in captivity. The female 

 laid 120 eggs, which hatched in eight hours, and the maggots lived five 

 days before transforming. The pupa or cocoon stage also lasted five 



B G. H. F. Nuttall, Johns Hopkins Hospital Keports, Vol. VIII., p. 16. 

 8 L. O. Howard, Bureau of Entomology, Bull. 4, p. 46, 1896. 



