LIFE HISTORY 25 



portions of the substance in which they have been feed- 

 ing and transform in the cooler portions. He sug- 

 gests the idea that this migration outward may be a 

 provision for the more easy emergence of the fly when 

 the time should come. In some cases he found that the 

 pupal stage lasted through several weeks, but he was 

 never successful in keeping pupae through the winter. 

 Mr. Newstead found that in stable middens the puparia 

 occur chiefly at the sides or at the top of the wall or 

 framework of the receptacle where the temperature is 

 lowest. He found them in such situations often packed 

 together in large masses numbering many hundreds. 

 In ash pits he found the same conditions. 



Where the manure is in small piles, or is partly spread 

 out, the full-grown larvae almost ready for transforma- 

 tion are apt to migrate into the loose ground under the 

 pile or from the edges of the pile outwards, to trans- 

 form under nearby rubbish. This habit may have a 

 very important practical value, since municipal regu- 

 lations of individual stable practice in regard to the 

 removal of manure should take into consideration that 

 such removal at intervals longer than those required 

 for the larva to reach full growth may result in the 

 leaving of many puparia, except of course in cases 

 where especial receptacles for manure are in use. 



Emergence of the Adult 



This has been well described by Doctor Hewitt as 

 follows : 



''When about to emerge, the fly pushes off the an- 



