34 



BULLETIN 932, U. S. DEPARTMENT OF AGRICULTURE. 



black spot was 5.54 days, maximum 8 days, and minimum 3 days; 

 the average length of the incubation period was 7.22 days, maximum 

 11 days, and minimum 6 days. 



Laev.e of the Second Brood. 



Time of hatching. — By reference to Table XX it will be seen that 

 the time of hatching of eggs of the second brood extended over a 

 period of more than two months, namely, from July 19 to September 

 24. The largest number hatching in any one day was 2,280 on 

 August 21, a date which is just midway between that when the first 



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SEPTEMBER 



Fig. 9. — Time of hatching of eggs of the second brood of the codling moth, Grand 



Junction, Colo., 1915. 



larvae of this brood appeared and the date when the last larva 

 hatched. In figure 9 the daily hatching record is shown diagram- 

 matically with average daily temperatures. 



Length of the feeding period. — The length of the feeding period of 

 larvae of the second brood was established by means of the stock-jar 

 method (see p. 8). The observations of 1,939 larvae are presented 

 in Table XXI, in which it will be noted that the feeding periods 

 during the warmer weather of July and August were considerably 

 shorter than those during September and October. The first larvae 

 of the second brood entered the fruit July 19, and although some of 



