THE CANADIAN ENTOMOLOGIST 75 



A few puparia were found directly beneath the manure pile 

 to a depth of twelve inches. The greatest numbers occurred in 

 the region about eighteen inches from the pile and at a depth of 

 twelve inches to two feet from the surface; this is graphically 

 shown in the figure; the puparia were also numerous immediately 

 below the surface of the soil. The numbers then gradually de- 

 creased proportional to the distance from the pile and dwindled 

 away at a distance of about four feet from its base.- 



This observation is of practical interest to the sanitarian as 

 indicating the habits of the larv^ae under normal conditions. It 

 illustrates the ability of the flies to emerge from a depth of two 

 feet, as particular attention was paid to condition of the puparia, 

 and the flies had emerged from all the puparia other than those 

 that had failed to develop. 



The Ovenointering of the House-fly 



The question as to the state in which Miisca domestica passes 

 the winter has been discussed recently by several workers, and it 

 seems desirable to review the subject again in so far as my. ex- 

 perience of conditions in the most northerly temperate latitudes 

 of England and Canada are concerned. In my monograph on the 

 house-fly (1914) the statement is made that three causes con- 

 tribute to the disappearance of the flies at the end of the summer, 

 namely, retreat into hibernating quarters or into permanently 

 heated places, natural death, and death from EmpusamusccE. I 

 must confess that the word "hibernation" has been used in too 

 broad a sense by me, as it has not only implied a dormant state 

 during the winter, which is the usually accepted meaning of the 

 term, but it has also had reference to a possible and sometimes 

 actual state of activity during the winter months. It is in this 

 sense that the word "hibernation" was used, as will be gathered 

 in reading the section under that heading, in the work referred to. 

 It would be preferable to substitute the term "overwintering," as 

 this will adequately cover all conditions and developmental stages 

 and will avoid a possible misuse of the term "hibernation." 



Taking all the evidence that is now available, it may be 

 stated that in northerly latitudes Musca domestica exists in the 

 overwintering period in the following states: 



