325 



An Example of Estimation of Seasonal Progress. 



The example below, which is designed to show the method of predic- 

 tion, is based upon Glenn's observations of band collections at Olney for 

 1916, as shown in his Table 33.* 



His observation showed that the first pupa appeared April 13, and 

 that the maximum pupation was April 20. As the preceding autumn and 

 winter had a total rainfall of slightly more than 20 inches, the develop- 

 mental total should be 0360 (Table III), and the first moths would be 

 expected to emerge May 13 — the date on which that total was reached 

 (using velocity values from Table I for the temperatures and humidities 

 as shown in Glenn's hygrothermograph records April and May, 1916). 

 The individual variation would throw it back about two days : the actual 

 time of first emergence was May 11. The day of maximum emergence, 

 reckoned from the date of maximum pupation, should fall on May 19, 

 which was the date observed. 



According to Isely and Ackerman, egg-laying is controlled by the 

 temperatures after sunset, taking place in very faint light and above 

 02° F. In the absence of data on cloudiness and temperature immediately 

 after sunset in May, 1916, we may take the average time as two days for 

 the period from emergence until laying is well begun. On this basis, the 

 first eggs should have been laid on the 1-lth. The actual date observed was 

 the 14th. The normal incubation total of 3864 developmental units was 

 reached on May 25 early in the morning. The actual 'time of hatching 

 observed was May 25. (The correction of 8% for individual variation 

 would throw some hatching back to sunset of May 24.) 



Pupation should occur when a normal total of 18,000 developmental 

 units (reckoned from the time of hatching of the eggs) is reached, if the 

 rainfall is normal for that period. (An average of 6.66 inches was used 

 as the normal in calculation of standard time.) It may be later or earlier, 

 accordingly as the period in the apple comes at a time with more or less 

 rainfall. \\'ith 10.6 inches of rainfall during this period in 1916, we 

 should expect a maximum pupation when a total of approximately 19,000 

 developmental units was reached, that is, on June 30. Individual varia- 

 tion in larval time (16%) would permit some larvae to pupate six days 

 earlier (June 24). 



Counting from June 24, with velocity values from Table I, we get a 

 total of 6480 developmental units on July 5. The correction for individual 

 variation throws the probable date for first emergence of the adult moth 

 one dav earlier, or July 4. The first adult actually emerged on July 3. 



The first eggs of the second generation should be laid on the 6th. 

 That was also the date observed. A total of 3864 developmental units 

 was reached on the 12th; the actual first larva was observed on the 12th. 

 (The 8% correction for individual variation of the egg amounts to about 

 half a day.) 



I 

 I 



' These data were not used in establishing velocity values. 



