400 



270) is 21.7 days for the May lot and 20 days for the August lot, the 

 observed times being 21 and 17 days respectively. No modification of 

 the velocity chart consistent with the experimental or i)henological work 

 will correct all these differences. The cause of the ditf'erences is to be 

 sought in other conditions and will be taken up later in connection with 

 effects of temperature variability. 



Above first line; first generation 1917. 



Above second line; hibernated generation 1918. 



Air velocity 8 mm. per sec. except 203DK, BDK which was + . The italic cap- 

 itals indicated light condition. 



Below second line; hibernated generation 1918, out of doors, segregated into tem- 

 perature classes. Air movement was not recorded. 



