58 BULLETIN 1235, U. S. DEPARTMENT OF AGRICULTURE. 



rainy weather. Thereafter the weather was not unusually warm 

 until the last week in August, when temperatures of 100° F. or more 

 were again experienced for five or six days. With a cooler spring, 

 the development of trees was delayed, and apples were not in full 

 bloom until about the beginning of May, nearlv two weeks later than 

 in 1915. 



Figure 34 summarizes the data secured on several of the stages 

 of the codling moth in 1916. Pupation was at a maximum on April 

 26, and the average length of the pupal stage was 31.29 days. Moths 

 of the spring brood began emerging in the orchards early in May, 

 though none was secured at the msectary from the limited material 

 available until May 20. There was a maximum emergence on May 

 24, and emergence continued until June 17, though, owing to the 

 cool weather of the latter part of June, a few moths emerged in the 

 orchards as late as July 11. Only general observations were made 

 on oviposition, and this work began late in May and continued as 

 long as moths were present. 



Larvae of the first brood began leaving the fruit on July 5. On 

 July 11 an examination was made of 687 wormy apples, and it was 

 found that the mature larvae had gone from 5.6 per cent of these. 

 The largest number left the fruit on August 3, and larvae continued 

 to leave until August 24. The average cocooning period for 493 

 first-brood larvae was 6.42 days. Pupation occurred from July 12 

 until August 29, with a maximum on July 31, as shown in Figure 34. 

 The average pupal period of 493 first-brood pupae was 13.49 days. 



Moths of the first brood were emerging from July 24 until Septem- 

 ber 14, and probably later, with a maximum on August 15, and 

 the oviposition followed very closely the emergence of the moths. 

 The maximum hatching of second-brood larvae occurred August 

 15 to 20. 



It will be seen from this brief summary that the life history of 

 the codling moth in the Wenatchee Valley follows very closely that 

 in the Yakima Valley, but each period would probably occur slightly 

 later in the same year at Wenatchee than at Yakima. 



MISCELLANEOUS STUDIES. 



WINTERKILLING OF LARVAE. 



It is a common occurrence to find winterkilled codling moth 

 larvae when examining trees in the spring. Some larvae appear to 

 succumb to fewer degrees of cold than others, but, as the cold increases, 

 increasing numbers of larvae are killed. An opportunity of studying 

 this effect of the cold was afforded in the winter of 1919-1920. In 

 December, 1919, minimum temperatures were experienced in the 

 Yakima Valley lower than any previously recorded. On December 

 9 and 10, a severe snowstorm occurred, with some wind. The 

 storm cleared away on the 11th, and minimum temperatures of 

 zero or lower were recorded for the four succeeding days. On 

 December 13 the Weather Bureau observer at Yakima reported 



— 24° F. while the minimum thermometer at the insectary recorded 



— 25.5° F. Unofficial reports from various points in the Yakima 

 Valley showed minimum temperatures of —15° to —30° F. During 

 this cold period there were from 4 to 18 inches of snow on the ground. 



