J. E. M. Mkllor 57 



the winter in the pupal state, as is the case with certain Anthomyidae^^] 

 and (1914, p. 107) has kept Slonioxi/s calcifrans over winter as pupae; 

 but thinks that M. domestica only winters in the adult stage. He points 

 out that the abdomens of those caught in winter are full of fat and that 

 the alimentary canal is shrivelled up. He writes (1915) that he has 

 always held the view suggested by Copeman and Austen (1914) "that 

 the relative lateness of the season at which house-flies annually become 

 abundant may be due to the smallness of the numbers of individuals 

 that in an active, or inactive condition, survive the winter in houses or 

 buildings." 



Graham-Smith (1914), summarising the opinions on this subject up 

 to 1914, wrote that "flies may be found active throughout the winter 

 in relatively high temperature, e.g. warmed houses, kitchens, bake- 

 houses, and in the presence of sufficient food material may even con- 

 tinue to breed, but little is known as to their method of passing the 

 winter under natural conditions. Most observers, however, seem to 

 think that the winter is passed in the adult condition." 



In Group II may be placed Jepson (1909) and Copeman (1913). The 

 former considered that autumn flies were hardier than summer ones, 

 and found them in kitchens at temperatures of 65° F.-80° F. "quite as 

 active as in summer," and persuaded them to breed and oviposit on 

 soaked bread. He also found sluggish specimens behind books on a 

 bookshelf in December and January; but failed to bring 200 pupae alive 

 through the winter. 



The latter wrote " as to whether flies can persist through the winter in 

 other than the adult form practically nothing is known ; but as the eggs 

 and larval stages, at any rate, appear to be less resistant to the effects of 

 reduction of temperature than the fly itself, it is probable that the 

 progeny of the later broods, for the most part, never arrive at maturity, 

 both eggs and larvae perishing in their breeding places," and that, 

 though it would seem that the pupae might stand the winter better than 

 the earlier stages, he knew of no instance of their having been success- 

 fully wintered. The examination of the thatch of a hen house in March 

 1913, of tw^o attics in March and May respectively, and of 25 hay and 

 corn stacks in April showed the complete absence of M. domestica in 

 those places. And Austen, who identified the specimens collected, re- 

 marked, of those which were found, that the predominance of females to 

 males was so slight as to be practically negligible; and was not what 

 one would expect from hibernating flies. 



In Group III appear Williston (1908), Howard (1911 and 1912), 



