58 THE HOUSE FLY— DISEASE CARRIER 



the spray must be thinly appHed. The best result 

 reached by this method was ten days. The reverse, 

 namely, spraying with alcohol and shellac and then 

 dusting with rice powder, was satisfactory where the 

 shellac was not applied too thickly. Colored chalks 

 gave very satisfactory results, yellow and brick red 

 being the best ; the yellow lasting for nine days and the 

 brick red for twenty days. 



Length of Life of the Adult 



It seems that in midsummer the adult flies do not 

 live long, and it is extremely difficult to keep them 

 for any length of time in an enclosure, which, of course, 

 is the only true way of ascertaining exact age. At this 

 time of the year, flies die rapidly in confinement. In 

 June, 1898, the writer was unable to keep alive flies 

 collected at large and placed under a gauze enclosure 

 three feet cube for more than three days, but of course 

 this experiment meant nothing, since the age of the 

 flies collected was not known. Mr. Hine is convinced 

 that flies do not live a great many days in warm sum- 

 mer weather. Marked flies in his experiments in Au- 

 gust were not to be found after the third day, and in 

 his experiments with individuals, in confinement with 

 all necessary food, he was unable to keep them alive for 

 more than twelve days. He mentions an instance where 

 on a farm at Ira, Ohio, a pile of infested manure at 

 the barn was hauled up and spread in a field a quarter 

 of a mile away on August 15th; the occupants of the 

 house stated that there was a notable reduction in the 



