July, 1914.] THE APPLE MAGGOT. 83 



may transform several days earlier than this. The latest date 

 was November 27, 1909, the variety of apple being GiUiflower. 



The majority of individuals pupate in July, August and the 

 early part of September, in the latitude of southern New Hamp- 

 shire. 



DURATION OF THE PUPAL STAGE. 



The length of the pupal stage is variable between wide limits. 

 As will be described later, a point of separation between indi- 

 viduals occurs at this stage in the life history . A proportion of 

 individuals complete the pupal stage in approximately 300 days, 

 giving the one-year life cycle hitherto considered characteristic 

 of the species. Another proportion may remain in the pupal 

 stage for an extra twelve months, giving a two-year life cycle. 

 The data on which these findings are based will be found in 

 detail below. 



ONE-YEAR LIFE CYCLE. 



The duration of the pupal stage, in the case of individuals 

 that complete their life round in one year, apparently approxi- 

 mates 300 days, but may vary thirty days or more in either 

 direction from this figure. General conclusions are not possible 

 from the records in hand as to an average or the extremes. The 

 minimum pupal stage observed was 272 days, and the maximum 

 339 days. With pupation occurring actively throughout two 

 months and to some extent through two more, and with emer- 

 gence of adults actively in progress for about one month, there 

 is evident ground for a varying duration of this stage. 



Records of the duration of the pupal stage with individuals 

 of the one-year cycle will be found below in Table 24. 



Observations were not forthcoming to show that pupae from 

 late maturing larvae necessarily transform late the following 

 season. On occasion at least they may transform early. Among 

 the early emerging flies noted were some from comparatively 

 late pupae. 



However, in other instances, it was observed that the emergence 

 of adults from pupae that had their origin in very early fruit clearly 

 began early and reached a maximum somewhat early in the 

 season. In Table 4 it will be noted that the records of emergence 

 in the first and third columns are from early apples in which 

 pupation was occurring early in the season. The records in the 



