284 
Generally, larve that mature prior to August 1 transform; those that 
mature after September 1, hibernate; and of those that mature during 
August some hibernate and some transform, the percentage of those that 
hibernate usually increasing as the month advances, the rate of increase 
depending upon the temperatures. 
The time when hibernation takes place is determined largely by 
the habit of the species, but it may be somewhat modified by tempera- 
tures. While at Olney hibernation did not usually take place until Au- 
gust, a few unusually cool days caused some larve to hibernate as early 
as the first week in July in 1915, and in 1916 hibernation was delayed 
till the middle of August by continuous warm weather. Some larve 
hibernate any time after midsummer when the minimum daily tempera- 
tures fall to 60° or below and the mean daily temperatures to about 
70° or below; other larve do not hibernate until such temperatures have 
prevailed for two or three weeks. During the latter half of August 
hibernation is induced much more readily than earlier in the month, and 
with rare exceptions larve maturing after September 1 hibernate irrespec- 
tive of temperatures. _ 
Table 46 illustrates what has just been said concerning hibernation. 
Note that in 1915, 4.4 per cent. of the larvee which matured during 
the period from July 4 to July 7, at the close of a week of unusually cool 
weather, hibernated. Another period of cool weather ended with July 
25, and 5 per cent. of the larve maturing during the period from July 
25 to July 28 hibernated. The next period of cool weather began Au- 
gust 4, and 7 per cent. of the larve maturing during the period from 
August 4 to August 7 hibernated. From this time on, the mean daily 
temperatures remained near 70° or below, and the percentage of hiber- 
nating larve increased very rapidly until August 27. All larve under 
observation maturing after this date hibernated with the exception of two. 
The two larvee which transformed, matured during a period of twelve 
exceptionally warm days following September 7. 
In 1916 there were no cool days in July and none in August until 
the 14th. No larve hibernated in July. A few that hibernated prior to 
August 14, hibernated apparently purely from habit. The two cool days 
of August 14 and 15 may have hastened hibernation, but the percentage 
of those that hibernated increased rapidly from the 16th to the 22d, 
although the weather was unusually warm, showing that after the middle 
of August larve will yield to their habit regardless of temperatures. The 
delay in the time of hibernation in 1916, as compared with 1915, was 
undoubtedly due to the higher temperatures in 1916 during August. 
RELATION OF Humipity AND EVAPORATION TO THE RATE 
oF DEVELOPMENT OF THE CODLING-MOTH 
When we began the preliminary study of our accumulated data on 
this subject they indicated clearly that temperature was the controlling 
factor in determining the rate of development of the stages of the cod- 
ling-moth, and that humidity and evaporation had at most only a very 
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