122 MASS. EXPERIMENT STATION BULLETIN 211. 



' Records stopped June 1. See p. 108. 



Summer production includes June, July, August and September. The 

 sharp decline previously noted is checked, and the mean monthly produc- 

 tion declines much more gradually from month to month till October. 

 Some years the decline is less than others (see Table V) . The decline dur- 

 ing the summer is due to the completion of the annual cycle on the part of 

 some individuals, the first cases occurring in June, and to some slackening 

 in rate (intensity) . As shown in Table IV, there has been some increase in 



Table V. — Decrease in Mean Monthly Production from Highest Monthly 

 Mean {March or April) to Jxme, and from June to September. 



summer production in the high line over the earlier years. It is believed 

 that the elimination of broodiness will be the main factor in securing 

 further increase of production during these months. 



