December, '16] DOVE: WINTERING of HOUSE-FLY 531 



45° F. all adults were (luiescent; fed ones crawled slightly at 48° F., 

 could be forced to fly at 51° F. and would fly voluntarily at 53° F. 

 When voluntary flight occurred adults would feed if food was near, 

 but would not search for it. Eflorts were made to determine the 

 actual effective temperatures for adults. In working with specimens 

 motionless from cold the thermometer was placed on the ground with 

 them, and in other cases a suspended thermometer was used on which 

 adults alighted prior to the low temperatures. 



At Dallas, Texas, there is no long period of low temperatures during 

 which adults become altogether dormant. When freezing tempera- 

 tures do occur at night it is often warm enough at midday to permit 

 activity out of doors. The cold weather usually comes in the form of 

 "northers" and the temperature often drops 30° F. or more within 

 twelve hours. If, prior to a norther and on a fairly warm day, one 

 visits the city dumping grounds he will find numerous flies feeding 

 and occasionally depositing. Garbage wagons leaving during the 

 day will be carrying them to various portions of the city, though the 

 number is not to be compared with the greater number during the 

 summer months. Shortly after a norther and when outside tempera- 

 tures are warm enough to permit flight, if one again visits the dumping 

 grounds, not a living adult is to be found. Only adults in houses are 

 found alive and they are mostly in warm places and active. The 

 death of exposed adults under conditions as above outlined has been 

 proved by gradually warming those which were found inactive and 

 unprotected from cold. 



In general it may be said that the longevity of adult house-flies 

 varies indirectly with decreases in temperature provided they have 

 suffi.cient food, are not subjected to freezing temperatures and are not 

 killed by Empusa 7nusca\ Should they be prevented from following 

 their natural tendency to seek temperatures above 60° F., the humidity 

 being normal, the adults become inactive at 45° F. But since the 

 temperatures vary in different places, either naturally or by man's 

 interference, adults do not generally remain quiescent. They seek the 

 warmer temperatures and their longevity is correspondingly decreased. 



Possible Relation Between the Development of Empusa Muscle 



AND OvIPOSITION 



In the spring of 1915 a number of specimens of Lucilia sericata, all of 

 which had emerged from the same infested meat, were placed in dis- 

 infected cages. Fresh bananas were supplied in all cages. In an 

 attempt to determine the eff'ect of a lack of deposition media on the 

 longevity, some adults developed a fungus. This was first observed 

 among females, but only in the cage where meat was not supplied for 



