Apr. 15. i9i8 Overwintering of the House Fly 151 



IN PROTECTED OR SLIGHTLY HEATED LOCATIONS I 



An attempt was made to test experimentally the prevailing idea that 

 house flies can pass the winter in cracks and crevices in protected places 

 of houses and stables. A portion of one of the bams of the Arlington 

 farm was selected. The barn is a two-story structure, the first floor of 

 which has stalls for 25 horses, a carriage room, and harness room. On 

 the second floor are storage spaces for hay and grain, and at one end over 

 the carriage room is the farm office. Steam pipes conducting heat to 

 this office pass under the concrete floor of the carriage room and up inside 

 the wall of the harness room. The carriage room has large doors on the 

 south side and three windows on the north. A certain amount of heat 

 is given off from the steam pipes in the harness room and through the 

 floor so that the temperature is modified and does not fluctuate as much 

 or as rapidly as does the outdoor temperature. A shelf was constructed 

 in the carriage room about 5 feet from the floor and some distance away 

 from both the steam pipes and the windows. Fly cages were kept on 

 this shelf, and a thermograph was installed. 



Of several experiments conducted here the following two gave the best 

 results : 



Experiment No. 13. — Sixty-five flies (45 males and 22 females), which had been 

 reared in the greenhouse, emerged between December 26 and December 28, 1914. 

 They were transferred to wire cages and supplied with banana and a mixture of bran 

 and fresh horse manure well moistened. This material was renewed from time to 

 time as needed. The cage was put on the shelf in the stable on December 29 and was 

 examined every other day after this date. The flies died, a few at a time, up to March 

 9, 191 5, when the last ones (9 males and 8 females) were found dead. In this experi- 

 ment, then, 17 flies had been kept alive for a period of from 70 to 72 days. The maxi- 

 mum temperature during this period was 62° and the minimum was 29°. The mean 

 temperature for the entire period was 43.8'^. 



Experiment No. 16. — From rearing experiments in the greenhouse 46 flies emerged 

 between January 28 and February 3, 191 5. These were transferred to a cage with the 

 same kind of food as in Experiment No. 13, and placed on the shelf in the stable on 

 February 3. The last fly of this lot, a male, was found dead on March 9, 1915, giving a 

 maximum longevity of from 41 to 47 days. They were subjected to the same tem- 

 peratTU-e conditions as obtained in experiment 13. 



The following season, experiments of a similar kind were conducted in 

 the attic of the apicultural laboratory of the Bureau of Entomology at 

 Dmmmond, Maryland. This attic has one large south room which is 

 plastered and heated. The heat Vv^as turned off and the door communi- 

 cating with the unplastered part was left open. Cages were kept on a 

 table in this room and the flies were supplied with banana and a sponge 

 soaked in a sugar solution. Maximum and minimum thermometers were 

 used in recording temperatures. 



The best results were obtained in experiments 60 and 61 following: 

 Experiment No. 60.— House-fly puparia were collected on November n, 1915. 

 Twenty flies, emerged between November 13 and 16, were transferred to a cage and 



