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reflected in a corresponding drop in the pupation of the second 

 generation at that time, and the next drop in temperature beyond 

 the middle of that month shows most conspicuously in the number 

 of eggs laid and in the sudden drop in the number of moths emerg- 

 ing; and finally, the September figure of temperature changes is 

 copied in practically every detail by the figure showing the rate at 

 which the full-grown apple-worms were escaping from the apples. 

 As the thermometer warms up their number increases, and as it 

 falls their number diminishes, and so again and again to the end 

 of the season. 



It will be noticed that it was quite impossible to distinguish the 

 second and third generations by means of the band records only. 

 The larvae of the third generation began to come out of the apple long 

 before those of the second generation had all escaped, and the highest 

 numbers taken under bands were made up from these two generations 

 indiscriminately. 



Besides this diagrammatic illustration of the effect of tempera- 

 ture on life history, we have some facts which may be given in 

 the more precise form of numbers. Comparing the hatching periods 

 of two large lots of codling-moth eggs, one of which was laid in 

 early May and the other in late July, we find that the time re- 

 quired for the hatching of the July eggs averaged seven and two 

 thirds days less than the time required for the May eggs, while the 

 average temperature of the corresponding July days was 14.2 degrees 

 higher than the temperature of the corresponding days in May. 

 That is, as the average of temperature rose fourteen and two thirds 

 degrees the incubation of the egg was shortened by about half that 

 number of days ;• or, otherwise stated, two degrees of increased tem- 

 perature meant one day less in the egg. Next, comparing the pupal 

 periods of two lots of codling-moths, one of which lots formed the 

 pupa in late April and the other in late July, we find that the time 

 spent in the pupal stage was a little more than fourteen days 

 shorter in July than in April; while the corresponding July tem- 

 peratures averaged a little more than fourteen degrees higher than 

 the April temperatures. That is, as the average of temperature 

 advanced one degree the pupal period was shortened by about 

 one day. It may seem strange, at first thought, that it should re- 

 quire two additional degrees of heat to shorten the egg period by 

 a day and only one additional degree to take a day off the pupal 

 period, but the pupal period is, in fact, about twice as long as the 

 egg period at the same temperatures, and a change of a degree in 

 temperature changes each in approximately the same ratio. A rise 

 in temperature which will shorten the egg period by one fifth of its 

 length would shorten the pupal period also by about a fifth. 



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