3:^0 



These first larvae of the second generation were in the apples during 

 a period with 1.5 inches of rain, which would fix the total at 16,615 

 development units. This was reached on August 7. With a deduction 

 of 4 days for individual variation, the earliest probable date for first 

 pupation becomes August 3. The earliest actual date recorded was 

 August 9. Reckoning from August 3, we should expect the moths to 

 emerge on August 12, when 6480 developmental units had accumulated. 

 With the individual-variation correction of one day, the date becomes the 

 11th. One adult actually appeared August 12, and others followed 

 closely, indicating that some pupae were overlooked. Not knowing the 

 light and temperature after sunset, we would say that some eggs should 

 have been laid August 14, but none were actually found until the 19th ; 

 and we should expect hatching on August 20, but no larvae were observed 

 before August 23. This indicates the need of further study of egg-laying 

 and the recording of conditions necessary for egg-laying. 



Abuxdance of Late-Pupating Larvae in Spring. 



It has been supposed by some investigators that the delay in pupation 

 on the part of some larvae in spring is due to external conditions. A 

 large series of larvae were hibernated and the moths brought to emergence 

 under the same condition. (For methods used, see pp. 405 ff.) The 

 results were the same, or essentially so, for the larvae that were soaked 

 in water and those that were merely kept in moist air. The pupations 

 were strung out over a long period, the last emergence being 28 days after 

 the first, at a constant temperature of 72° F. (See Fig. 25, p. 409.) 

 The curve of emergences shown in Fig. 25 B has one main maximum 

 which falls on the 8th day, and also a group of three small maxima center- 

 ing on the 22d day (72° F.). If such a group is large, as it is likely to 

 be when larvae hibernate in abundance, it may be responsible for damage 

 to apples on trees sprayed to meet the early large group. 



The velocity units for larvae in the apple (Table V, p. 323) may 

 probably be used, with fair results, to estimate the time of the late pupa- 

 tion ; because the variation in the emergence of moths is determined pri- 

 marily by the time of pupation, or in other words by delay in larval 

 development. 



In the experiments the main maximum emergence came after the 

 accumulation of 4,704 developmental units, the next maximum after an 

 accumulation of 6,480 units, and the center of the last group after an 

 acctmiulation of 12,936 units. The center of the last group of spring 

 pupations at Olney in 1915 came after an accumulation of 16,152 units; 

 in 1916, of 15,888; and in 1917, of 13.008. These years average 15,024 

 developmental units for the period. This means that the late group of 

 pupations falls three to five weeks later than the first pupation. This 

 marks the starting point of the pupal stage of the late group, and from 

 this point the date of emergence of the moths may be fairly accurately 

 determined as already indicated. Other maxima occur for pupation, but 



