THE CODLING MOTH IN THE YAKIMA VALLEY. 



75 



Table 63. — Summary of the -phases in the life of the adult codling moth, Yakima, 

 Wash., 1919-1921— Continued. 



Phase and year. 



Minimum. 



Average. 



Maximum. 



Number of eggs per female moth of the first brood: 



1919 : 



1 



23.39 

 21.96 

 20.39 



13.97 

 13. 87 

 11.72 



13.08 

 13.24 

 11.39 



173 



1920 





1921 







Length of life of male moths of the first brood: 



1919 - 



2 

 2 



1 



1 

 1 



1 



45 



1920 



34 



1921 



39 



Length of life of female moths of the first brood : 



1919 



37 



1920 



10 



1921 



50 







Studies of certain phases of the seasonal history of the codling 

 moth in the upper and lower Yakima Valleys indicate that the 

 spring brood of moths appears in both valleys at about the same 

 tune, but that the majority of the mature larvae of the first brood 

 are leaving the apples from a week to two weeks earlier in the lower 

 valley. 



Incomplete seasonal history data recorded at Wenatchee, Wash., 

 in 1915 and 1916 indicate that the life cycle of the codling moth is 

 approximately the same at Wenatchee as at Yakima. 



A winter temperature of —25° F. or colder may kill all the codling 

 moth larvae above snow line, a temperature of —20° to —25° F. 

 may kill 80 to 90 per cent of the larvae, a temperature of —15° to 

 — 20° F. may kill 70 to 80 per cent, while a temperature of only — 7° 

 or — 8° F. kills only about 4 per cent of the wintering larvae. 



Moths of the spring brood emerging from cocoons spun in the soil 

 may appear from 1 to 9 days later than those from cocoons above 

 ground, although in 1922 they appeared earlier on the average. 



Most of the moths of the spring brood emerge in the morning, 

 two-thirds of them appearing between 9 a. m. and noon. Moths of 

 the first brood emerge over a longer period of the day, but the 

 majority of them appear before the maximum temperature for the 

 day is reached. 



Female moths of the spring brood deposit 65 to 80 per cent of their 

 eggs between the hours of 3 p. m. and 9 p. m., most of these being 

 deposited before 6 p. m. Very few eggs are deposited unless the 

 temperature is 60° F. or higher. Female moths of the first brood 

 also deposit a great majority of their eggs between 3 p. m. and 9 p. m., 

 but owing to the higher temperatures most of these eggs are deposited 

 after 6 p. m. 



From oviposition records obtained from individual female moths 

 of the spring brood it appears that the moths may lay as many as 94 

 eggs, while others will lay none, the average being 14. Moths of the 

 first brood deposit twice as many eggs, the number ranging from none 

 to 173, with an average of 30. 



The codling moth larva emerges from the egg through an opening 

 made in the periphery, never through the portion of the eggshell 

 adhering to the fruit or leaf. 



The date of hatching of the earliest larvae of the first brood varied 

 as much as 11 days in the three years the codling moth was under 



