48 



usually parallel with that of the temperature, hut toward the end of 

 the record the temperature has but little inlluence. The record made 

 by Mr. Georg-e (fig. T) and Mr. Ayers (figs, 8 and 9) show practically 



Fig. 8.— Weekly band record made by Mr. Ayers at Boise, Idaho, in 1897, on 1-10 trees. 



the same conditions, but not so clearl}', on account of the length of 

 time between the observations. 



LENGTH OF THE LIFE CYCLE. 



In order to establish a correct basis for the determination of the 

 number of generations, it is essential that we determine as closely as 



Fig. 9.— Band record made by Mr. Ayer.s in 1898. 



possible the average number of days in which the insect can pass 

 through one generation. Assuming a certain date, with as much 

 accuracy as possible, when the maxima occur in a band record, and 

 taking into consideration all the imperfections of the records, we 

 should have approximately in the number of days between these max- 



