20 



BULLETIN 932, U. S. DEPARTMENT OF AGRICULTURE. 



Length of incubation.— As will be noted in Table VIII, the earliest 

 eggs required an incubation period about twice as long as those de- 

 posited later. This is accounted for by the lower temperatures to 

 which the earlier eggs were subjected. The incubation period 

 gradually decreased as the daily temperatures became higher with 

 the advance of the season. The average number of days from the 

 date of deposition to the time of the appearance of the red ring was 

 2.70, maximum 9 days, minimum 1 day ; the average number of days 

 from the date of deposition to the black-spot stage was 6.62, maxi- 

 mum 13 days, minimum 4 days; the average incubation period was 

 9.14 days, maximum 15 clays, minimum 6 days. 



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Fig. 4. — Time of hatching of eggs of the first brood of the codling moth, Grand 



Junction, Colo., 1915. 



~Lab.vm of the First Beood. 



Time of hatching.— Larvae of the first brood commenced to hatch 

 on Miay 27 and continued to hatch until July 13, as given in the com- 

 plete hatching data in Table VIII. The eggs were hatching in 

 maximum numbers on June IT, just one week after the time when the 

 greatest number of eggs was deposited. The interval from the date 

 of the appearance of the first larva to the time of hatching of the 

 larvae in maximum numbers was 21 days. This interval would prob- 

 ably have been reduced somewhat had the weather been warmer on 

 June 12, 13, and 14. The time of hatching of the eggs of the first 

 brood is presented graphically in figure 4. 



Length of the feeding period, stock-jar method. — The length of 

 the feeding period of 758 larvae of the first brood (both transforming 



