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, 
