5IO Bulletin 78 



In an hour or two after the puparium is formed, the skin begins to turn 

 brown, and usually reaches a light cinnamon color in eight or nine hours. 

 Some do not get much darker, but others pass to a dark seal brown color. 

 They vary considerably in size, some being a third smaller than others. It 

 was at first thought that this might be a sexual difference, but both sexes of 

 the flies emerged from some of the smallest ones isolated for the purpose. 



The duration of the pupa stage is stated by most authors to 

 vary from two to three weeks in the summer. Mr. Whitehead 

 says sixteen days. Dr. Riley records the appearance of the flies 

 after only eight days of pupation. Most of the puparia under our 

 observation gave out the flies in about twenty days, in June ; 

 with some it lasted only fifteen days, with quite a number nearly 

 two months, with others three months, and from a few the flies 

 had not emerged by September 5, or three and a half months after 

 the puparia were formed. These are very surprising facts when 

 one understands that all of these purparia came from the first 

 brood of maggots. There is no hint in the literature of any such 

 retardation in development. Yet our observations are conclusive. 



For instance, nine puparia were put in a tumbler May 23, and flics 

 emerged and were removed on the following dates, one on June 7, one on 

 June 8, three on June 10, one on June 14, one on August 18, and one on 

 August 23 ; one puparium was opened August 18 and it contained a fly pupa. 

 These dates also correspond very closely with our notes on the appearance of 

 the flies in our larger cages (figure 10), where hundreds of them emerged 

 during the summer. 



This state of affairs complicates matters, especially as regards the later 

 broods of the pest. It is even possible that some of the first brood of puparia 

 hibernate. We comment further on this phase of the subject when we dis- 

 cuss the number of broods of the insect. 



Habits of the flies in summer. — When the pupa is fully mature, 

 it crowds against one end of its brown home, which soon splits 

 open and allows the fly to emerge. As Dr. Fitch says, it " crawls 

 up out of the ground, with its wings crumpled up, and climbing 

 up the side of a clod or any perpendicular surface which it finds, 

 these members expand and assume their proper form before they 

 become dried and firm." The flies are frequently to be seen rest- 

 ing quietly for several minutes at a time on different parts of the 

 food-plants of the maggots. As the Anthomyiians frequent 

 flowers, doubtless the cabbage fly will be found on the various 

 blossoms growing in or near gardens during the summer. 



