255 
tion of effective day-degrees was 86 greater during the period of larve 
reared in apples on the tree than during the period of larve reared in 
picked fruit. Since the average daily accumlation of day-degrees shown 
in these tables is approximately 22.75, the difference in day-dgrees repre- 
sents a difference of about 4 days in the period. That is, larve of the 
first generation may be expected to mature, on an average, about 4 days 
earlier in picked fruit than in fruit on the tree. The difference of 6.7 
days shown above is, therefore, partly due to differences in temperature 
as well as to difference in the condition of the fruit in which the larvee 
fed. 
The period of transforming larve of the second generation varied 
from a maximum of 33 days in the fruit and 7 days in the cocoon to a 
minimum of 17 days in the fruit and 1 day in the cocoon, the average 
period in the fruit being 22.6 days and in the cocoon 4.2 days. The 
average total period for 36 males was 26.3 and for 59 females 27.4, the 
average for both being 26.8 days. The larval period of the female was 
about one day longer than that of the male. 
Hibernating larvae—In treating the larve of the hibernating genera- 
tion no distinction has been made between larve of the different genera- 
tions of the season which compose it. The period of the larve varied 
from a maximum of 46 days in the fruit and 269 days in the cocoon ta 
a minimum of 16 days in the fruit and 209 days in the cocoon, the average 
period in the fruit being 29.0 days and in the cocoon 236. The average 
total period of hibernating larvee was 264 for the males, 269 for the females 
and 265 for both males and females. 
The length of the larval period is affected by temperature and the 
character of food. It also varies in length in different individuals, even 
when they are under the same conditions as to temperature and food. 
The individual variations are well illustrated by the following examples. 
The periods of 16 larve which hatched on May 31, 1917, varied from 
25 to’ 33 days and the periods of 16 others which hatched June 11, 1917, 
varied from 24 to 38 days, though the environment of the individuals of 
each lot was as nearly the same as it was possible to have it. It is not 
infrequent that in lots of individuals kept under the same conditions as 
to light, food, heat, and moisture the variation in the period from the 
average for the group equals 30 per cent. of the average period. 
The relation of temperatures to the length of the larval period is 
shown in Tables 3 and 4, pp. 240, 243. A comparison of these two tables 
also shows that development is more rapid in picked apples than in apples 
on the tree. According to Table 3, at an average mean daily temperature 
of 74.31° F., the average period is 29.07 days in apples on the tree; and 
according to Table 4, at an average mean daily temperature of 74.08° F., 
the period is 25.69 days in picked fruit, or 3.4 days less than the period 
in apples on the tree. 
