152 Journal of Agricultural Research voi. xiii, no. 3 



placed on the table in the attic. Fresh food was supplied as needed, and a daily 

 watch was kept. The last flies of this lot died on January 4, 1916, thus living from 

 49 to 52 days. 



Experiment No. 61. — A similar experiment was conducted with flies which had 

 emerged on November 17 to 19, 1915. The last flies died on January 10, 1916. This 

 gives a longevity of from 52 to 54 days. The maximum temperature diu-ing this 

 period was 76°, the minimum 35°, and the mean, 56.9°. 



These experiments with caged flies in protected or slightly heated loca- 

 tions gave longevity records of 41, 47, 49, 52, 54, and 70 days. Dove 

 (5) ^ records an experiment at Dallas, Texas, in which a fly was kept 

 alive for 91 days in a large cage kept in an unoccupied room. In the 

 latitude of Washington it would be necessary for flies to live at least 

 from the first week of December (the time of the last emergence in the 

 fall) until early in April (when temperatures first are high enough to 

 induce oviposition) and be in condition to oviposit at the end of that time. 



IN HEATED BUILDINGS 



Overwintering experiments were also carried out in one of the warmest 

 rooms of the greenhouses at the Arlington Experimental Farm. The 

 room used was one in which tomatoes were grown, with temperatures 

 ranging as a rule from a minimum of 55° or 60° at night to about 80° 

 during the day. The humidity also was usually high. A few lots of 

 flies reared in experiments during the fall of 1914 were transferred to 

 this greenhouse at times during October and November. These flies 

 were kept in cages already described and supplied with banana and 

 fresh horse manure or a mixture of bran and horse manure. Eggs were 

 readily obtained except when the fungous disease Empusa muscae killed 

 off the adults too rapidly, and from the original lots of flies several 

 generations were reared during the course of the winter. Table II 

 gives the principal results of the experiments bearing upon the question 

 of how long the flies will live in heated rooms during the winter. 



In these experiments, where caged house flies were kept in a warm 

 humid atmosphere during the winter, longevity records of from 9 to 40 

 days were obtained. It will be noted from Table II that the short 

 records are all due to the attacks of Empusa muscae. There is, however, 

 no evidence that adult flies, even if they escape the attacks of the fungus, 

 can survive the wdnter in heated buildings. They were kept alive much 

 longer in places such as attics and stables, which were only slightly 

 heated. 



' Reference is made by number to "Literature cited" pp. 168-169. 



