48 
usuall}^ parallel with that of the temperature, but toward the end of 
the record the temperature has but little influence. The record made 
by Mr. George (fig-. 7) and Mr. Ayers (figs. 8 and 9) show practically 
\:^ 
Fig. 8. — Weekly band record made by Mr. Ayern at Boise, Idaho, in 1897, on 140 tree^. 
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. Ayers 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, ana 
taking into consideration all the imperfections of the records, wo 
should have approximately in the number of days between these max- 
