__ There was a considerable variation in the observed length of periods 
of individual pupe. Table 8 gives the distribution of pupz with respect 
i to the average accumulation of effective day-degrees of groups beginning 
the period on the same date. 
TABLE 8—Disrrisution or PurpAE WITH RESPECT TO THE AVERAGE ACCUMULATED 
EFFECTIVE DAY-DEGREES OF GROUPS BEGINNING THE PERIOD ON THE SAME DATE 
Number of pupe Day-degrees 
1 166 
if 185-194 
4 195-204 
3 205-214 
110 215-224 
602 225-234 
2238 235-244 
553 245-254 
170 255-264 
18 265-274 
7 ; 275-284 
qj 285-294 
2 : 295-304 
Recorded accumlations of less than 205 and more than 274 day- 
degrees are probably due to errors in observation. The lesser variations 
_ are probably due to individual differences, differences in humidity, and to 
the fact that the day was used as the unit in measuring time. The last 
factor mentioned may cause a variation of 27 from the average and is 
_ sufficient to account for nearly all of the variations. If we make a cor- 
rection in the variation due to the use of the day as the unit, we still 
i have left a variation of from 232 to 247 due to other causes, or a maxi- 
_ mum difference of 9 from the average, which is 241. 
