CONTROL OF HOUSEHOLD INSECTS 9 



records of a patient distributing these germs for 1 7 years and being 

 the incipient cause of 13 cases during 14 years of that period. Even 

 the urine of patients may contain active typhoid bacilli. Similarly, 

 the germs producing other intestinal disorders are discharged from 

 the system though presumably not persisting for such extended 

 periods. It is well known that the germ causing tuberculosis is 

 abundant in the sputum of patients. 



The house fly subsists entirely upon fluids and feeds with appar- 

 ently equal gusto upon fresh manure, decaying vegetable matter, 

 sputum or the daintiest culinary preparations. It is only neces- 

 sary for discharges from patients suffering from typhoid fever or 

 other intestinal diseases to be exposed in open vessels or poorly 

 constructed privies in order to secure the spread of the infection. 

 The hairy legs are fouled with thousands of deadly bacilli and 

 •countless numbers are swallowed. Shortly thereafter the flies may 

 appear in the house and incidentally contaminate the food, to the 

 great peril of the consumer, with the germs adhering to the limbs 

 and those deposited with undiminished virulence in the familiar fly 

 specks. This, while disgusting and abhorrent to every sense of 

 decency, occurs repeatedly in nature and is apparently ignored by 

 the masses, despite the deadly peril thus incurred. 



Habits. The house fly breeds by preference in horse manure, 

 though it lives to a limited extent in cow manure and miscellane- 

 ous collections of filth, especially decaying vegetable matter. The 

 flies deposit their eggs upon manure and similar material, the 

 young maggots hatching in less than 24 hours and, under favor- 

 able conditions, completing their growth in 5 to 7 days. The 

 maggots then transform to an oval, brown, resting or pupal stage, 

 remaining in this condition from 5 to 7 days. The life cycle is 

 therefore completed in 10 to 14 days, the shorter period being true 

 of the warmer parts of the year, particularly in the vicinity of 

 Washington, D. C. One fly may deposit 120 eggs, and as there 

 may be 10 or 12 generations in a season, it is not surprising that 

 this insect should become extremely abundant by midsummer. 

 Calculations show that, under favorable conditions, the descen- 

 dants from one fly might at the end of a season reach the stupen- 

 dous number of over 190 quintillion. It has been estimated that 

 1200 house flies might be bred from a pound of manure, and at 

 this rate a good load would produce two and one half million. 

 Fortunately, breeding is confined to the warmer months, only a 

 few flies wintering in houses in a more or less dormant condition. 



