42 THE HOUSE FLY— DISEASE CARRIER 



have been published are those made by Mr. F. P. Jep- 

 son, research student in medical entomology, Cam- 

 bridge University, England. According to Mr. Jepson 

 (1909), when the frosts come and the cold weather 

 begins in earnest, unprotected flies are probably killed. 

 Those which have found the shelter of some place like 

 a kitchen or a restaurant or a bake house, where the arti- 

 ficial temperature is sufficient unto their needs, continue 

 to live actively; and will even breed when conditions 

 are favorable. He states that some flies possibly exist 

 in dormant condition in such protected localities as be- 

 hind pictures and loose wallpaper. He found sluggish 

 specimens behind books on a bookshelf in December 

 and January and observed them for some time, find- 

 ing them in the same positions and still living a month 

 later. His observations ceased at the end of January, 

 but he saw no reason why they should not live on until 

 spring and then begin to breed. In the course of his 

 experiments he found that the flies occurring at the 

 close of the year are much more hardy than those oc- 

 curring in summer. This fact was experimentally 

 proved, as will be shown later. He further states that 

 one of his friends found flies, presumably typhoid flies, 

 to issue in large numbers from the empty frame of an 

 old window which was removed during the winter. 



Jepson experimented with the early stages, and, 

 knowing the idea that possibly the puparia hibernate, 

 he attempted to carry 200 pupae through the winter, 

 but without success. 



The most interesting part of his experimental work, 



